Many causes of autism have been proposed, but understanding of the theory of causation of autism and the other autism spectrum disorders (ASD) is incomplete. ASD is a complex developmental condition marked by persistent challenges to social interaction, speech and nonverbal communication, and restricted/repetitive behaviors. ASD phenotypes vary significantly.
Research indicates that genetic factors predominate. The heritability of autism, however, is complex, and it is typically unclear which genes are involved. In rare cases, autism is associated with agents that cause birth defects. Many other causes have been proposed.
Autism involves atypical brain development which often becomes apparent in behavior and social development before a child is three years old. It can be characterized by impairments in social interaction and communication, as well as restricted interests and stereotyped behavior, and the characterization is independent of any underlying neurological defects. Other characteristics include repetitive-like tasks seen in behavior and sensory interests. This article uses the terms autism and ASD to denote classical autism and the wider dispersion of symptoms and manifestations of autism, respectively.
Autism's theory of causation is incomplete. It has long been presumed that there is a common cause at the genetic, cognitive, and neural levels for autism's characteristic triad of symptoms. However, there is increasing suspicion among researchers that autism does not have a single cause, but is instead a complex disorder with a set of core aspects that have distinct causes. Different underlying brain dysfunctions have been hypothesized to result in the common symptoms of autism, just as completely different brain types result in intellectual disability. The terms autism or ASDs capture the wide range of its processes at work. Although these distinct causes have been hypothesized to often co-occur, it has also been suggested that the correlation between the causes has been exaggerated. The number of people known to have autism has increased dramatically since the 1980s, at least partly due to changes in diagnostic practice. It is unknown whether prevalence has increased as well.
The consensus among mainstream autism researchers is that genetic factors predominate. Environmental factors that have been claimed to contribute to autism or exacerbate its symptoms, or that may be important to consider in future research, include certain foods, infectious disease, heavy metals, solvents, diesel exhaust, PCBs, phthalates and phenols used in plastic products, pesticides, brominated flame retardants, alcohol, smoking, and illicit drugs. Among these factors, vaccines have attracted much attention, as parents may first become aware of autistic symptoms in their child around the time of a routine vaccination, and parental concern about vaccines has led to a decreasing uptake of childhood immunizations and an increasing likelihood of measles outbreaks. However, there is overwhelming scientific evidence showing no causal association between the measles-mumps-rubella (MMR) vaccine and autism, and there is no scientific evidence that the vaccine preservative thiomersal causes autism.
Genetic factors may be the most significant cause for autism spectrum disorders. Early studies of twins had estimated heritability to be over 90%, meaning that genetics explains over 90% of whether a child will develop autism. However, this may be an overestimation, as new twin studies estimate the heritability at between 60 and 90%. Many of the non-autistic co-twins had learning or social disabilities. For adult siblings the risk for having one or more features of the broader autism phenotype might be as high as 30%.
However, in spite of the strong heritability, most cases of ASD occur sporadically with no recent evidence of family history. It has been hypothesized that spontaneous de novo mutations in the father's sperm or mother's egg contribute to the likelihood of developing autism. There are two lines of evidence that support this hypothesis. First, individuals with autism have significantly reduced fecundity, they are 20 times less likely to have children than average, thus curtailing the persistence of mutations in ASD genes over multiple generations in a family. Second, the likelihood of having a child develop autism increases with advancing paternal age, and mutations in sperm gradually accumulate throughout a man's life.
The first genes to be definitively shown to contribute to risk for autism were found in the early 1990s by researchers looking at gender-specific forms of autism caused by mutations on the X chromosome. An expansion of the CGG trinucleotide repeat in the promoter of the gene FMR1 in boys causes fragile X syndrome, and at least 20% of boys with this mutation have behaviors consistent with autism spectrum disorder. Mutations that inactivate the gene MECP2 cause Rett syndrome, which is associated with autistic behaviors in girls, and in boys the mutation is embryonic lethal.
Besides these early examples, the role of de novo mutations in ASD first became evident when DNA microarray technologies reached sufficient resolution to allow the detection of copy number variation (CNV) in the human genome. CNVs are the most common type of structural variation in the genome, consisting of deletions and duplications of DNA that range in size from a kilobase to a few megabases. Microarray analysis has shown that de novo CNVs occur at a significantly higher rate in sporadic cases of autism as compared to the rate in their typically developing siblings and unrelated controls. A series of studies have shown that gene disrupting de novo CNVs occur approximately four times more frequently in ASD than in controls and contribute to approximately 5–10% of cases. Based on these studies, there are predicted to be 130–234 ASD-related CNV loci. The first whole genome sequencing study to comprehensively catalog de novo structural variation at a much higher resolution than DNA microarray studies has shown that the mutation rate is approximately 20% and not elevated in autism compared to sibling controls. However, structural variants in individuals with autism are much larger and four times more likely to disrupt genes, mirroring findings from CNV studies.
CNV studies were closely followed by exome sequencing studies, which sequence the 1–2% of the genome that codes for proteins (the "exome"). These studies found that de novo gene inactivating mutations were observed in approximately 20% of individuals with autism, compared to 10% of unaffected siblings, suggesting the etiology of ASD is driven by these mutations in around 10% of cases. There are predicted to be 350-450 genes that significantly increase susceptibility to ASDs when impacted by inactivating de novo mutations. A further 12% of cases are predicted to be caused by protein altering missense mutations that change an amino acid but do not inactivate a gene. Therefore, approximately 30% of individuals with autism have a spontaneous de novo large CNV that deletes or duplicates genes, or mutation that changes the amino acid code of an individual gene. A further 5–10% of cases have inherited structural variation at loci known to be associated with autism, and these known structural variants may arise de novo in the parents of affected children.
Tens of genes and CNVs have been definitively identified based on the observation of recurrent mutations in different individuals, and suggestive evidence has been found for over 100 others. The Simons Foundation Autism Research Initiative (SFARI) details the evidence for each genetic locus associated with autism.
These early gene and CNV findings have shown that the cognitive and behavioral features associated with each of the underlying mutations is variable. Each mutation is itself associated with a variety of clinical diagnoses, and can also be found in a small percentage of individuals with no clinical diagnosis. Thus the genetic disorders that comprise autism are not autism-specific. The mutations themselves are characterized by considerable variability in clinical outcome and typically only a subset of mutation carriers meet criteria for autism. This variable expressivity results in different individuals with the same mutation varying considerably in the severity of their observed particular trait.
The conclusion of these recent studies of de novo mutation is that the spectrum of autism is breaking up into quanta of individual disorders defined by genetics.
Epigenetic mechanisms may increase the risk of autism. Epigenetic changes occur as a result not of DNA sequence changes but of chromosomal histone modification or modification of the DNA bases. Such modifications are known to be affected by environmental factors, including nutrition, drugs, and mental stress. Interest has been expressed in imprinted regions on chromosomes 15q and 7q.
Most data supports a polygenic, epistatic model, meaning that the disorder is caused by two or more genes and that those genes are interacting in a complex manner. Several genes, between two and fifteen in number, have been identified and could potentially contribute to disease susceptibility. However, an exact determination of the cause of ASD has yet to be discovered and there probably is not one single genetic cause of any particular set of disorders, leading many researchers to believe that epigenetic mechanisms, such as genomic imprinting or epimutations, may play a major role.
Epigenetic mechanisms can contribute to disease phenotypes. Epigenetic modifications include DNA cytosine methylation and post-translational modifications to histones. These mechanisms contribute to regulating gene expression without changing the sequence of the DNA and may be influenced by exposure to environmental factors and may be heritable from parents. Rett syndrome and Fragile X syndrome (FXS) are single gene disorders related to ASD with overlapping symptoms that include deficient neurological development, impaired language and communication, difficulties in social interactions, and stereotyped hand gestures. It is not uncommon for a patient to be diagnosed with both ASD and Rett syndrome and/or FXS. Epigenetic regulatory mechanisms play the central role in pathogenesis of these two disorders. Rett syndrome is caused by a mutation in the gene that encodes methyl-CpG-binding protein (MECP2), one of the key epigenetic regulators of gene expression. MeCP2 binds methylated cytosine residues in DNA and interacts with complexes that remodel chromatin into repressive structures. On the other hand, FXS is caused by mutations that are both genetic and epigenetic. Expansion of the CGG repeat in the 5’-untranslated region of the FMR1 genes leads to susceptibility of epigenetic silencing, leading to loss of gene expression.
Genomic imprinting may also contribute to ASD. Genomic imprinting is another example of epigenetic regulation of gene expression. In this instance, the epigenetic modification(s) causes the offspring to express the maternal copy of a gene or the paternal copy of a gene, but not both. The imprinted gene is silenced through epigenetic mechanisms. Candidate genes and susceptibility alleles for autism are identified using a combination of techniques, including genome-wide and targeted analyses of allele sharing in sib-pairs, using association studies and transmission disequilibrium testing (TDT) of functional and/or positional candidate genes and examination of novel and recurrent cytogenetic aberrations. Results from numerous studies have identified several genomic regions known to be subject to imprinting, candidate genes, and gene-environment interactions. Particularly, chromosomes 15q and 7q appear to be epigenetic hotspots in contributing to ASD. Also, genes on the X chromosome may play an important role, as in Rett Syndrome.
The risk of autism is associated with several prenatal risk factors, including advanced age in either parent, diabetes, bleeding, and use of psychiatric drugs in the mother during pregnancy. Autism has been linked to birth defect agents acting during the first eight weeks from conception, though these cases are rare. If the mother of the child is dealing with autoimmune conditions or disorders while pregnant, it may affect if the child developed autism. All of these factors can cause inflammation or impair immune signaling in one way or another.
Prenatal viral infection has been called the principal non-genetic cause of autism. Prenatal exposure to rubella or cytomegalovirus activates the mother's immune response and may greatly increase the risk for autism in mice. Congenital rubella syndrome is the most convincing environmental cause of autism. Infection-associated immunological events in early pregnancy may affect neural development more than infections in late pregnancy, not only for autism, but also for psychiatric disorders of presumed neurodevelopmental origin, notably schizophrenia.
Teratogens are environmental agents that cause birth defects. Some agents that are theorized to cause birth defects have also been suggested as potential autism risk factors, although there is little to no scientific evidence to back such claims. These include exposure of the embryo to valproic acid, paracetamol, thalidomide or misoprostol. These cases are rare. Questions have also been raised whether ethanol (grain alcohol) increases autism risk, as part of fetal alcohol syndrome or alcohol-related birth defects. All known teratogens appear to act during the first eight weeks from conception, and though this does not exclude the possibility that autism can be initiated or affected later, it is strong evidence that autism arises very early in development.
Autoimmune and inflammatory diseasesEdit
Other maternal conditionsEdit
Thyroid problems that lead to thyroxine deficiency in the mother in weeks 8–12 of pregnancy have been postulated to produce changes in the fetal brain leading to autism. Thyroxine deficiencies can be caused by inadequate iodine in the diet, and by environmental agents that interfere with iodine uptake or act against thyroid hormones. Possible environmental agents include flavonoids in food, tobacco smoke, and most herbicides. This hypothesis has not been tested.
Diabetes in the mother during pregnancy is a significant risk factor for autism; a 2009 meta-analysis found that gestational diabetes was associated with a twofold increased risk. A 2014 review also found that maternal diabetes was significantly associated with an increased risk of ASD. Although diabetes causes metabolic and hormonal abnormalities and oxidative stress, no biological mechanism is known for the association between gestational diabetes and autism risk.
Maternal obesity during pregnancy may also increase the risk of autism, although further study is needed.
Other in uteroEdit
It has been hypothesized that folic acid taken during pregnancy could play a role in reducing cases of autism by modulating gene expression through an epigenetic mechanism. This hypothesis is supported by multiple studies.
Prenatal stress, consisting of exposure to life events or environmental factors that distress an expectant mother, has been hypothesized to contribute to autism, possibly as part of a gene-environment interaction. Autism has been reported to be associated with prenatal stress both with retrospective studies that examined stressors such as job loss and family discord, and with natural experiments involving prenatal exposure to storms; animal studies have reported that prenatal stress can disrupt brain development and produce behaviors resembling symptoms of autism. However, other studies have cast doubts on this association, notably population based studies in England and Sweden finding no link between stressful life events and ASD.
The fetal testosterone theory hypothesizes that higher levels of testosterone in the amniotic fluid of mothers pushes brain development towards improved ability to see patterns and analyze complex systems while diminishing communication and empathy, emphasizing "male" traits over "female", or in E-S theory terminology, emphasizing "systemizing" over "empathizing". One project has published several reports suggesting that high levels of fetal testosterone could produce behaviors relevant to those seen in autism.
Based in part on animal studies, diagnostic ultrasounds administered during pregnancy have been hypothesized to increase the child's risk of autism. This hypothesis is not supported by independently published research, and examination of children whose mothers received an ultrasound has failed to find evidence of harmful effects.
Some research suggests that maternal exposure to selective serotonin reuptake inhibitors during pregnancy is associated with an increased risk of autism, but it remains unclear whether there is a causal link between the two. There is evidence, for example, that this association may be an artifact of confounding by maternal mental illness.
Autism is associated with some perinatal and obstetric conditions. A 2007 review of risk factors found associated obstetric conditions that included low birth weight and gestation duration, and hypoxia during childbirth. This association does not demonstrate a causal relationship. As a result, an underlying cause could explain both autism and these associated conditions. There is growing evidence that perinatal exposure to air pollution may be a risk factor for autism, although this evidence suffers from methodological limitations, including a small number of studies and failure to control for potential confounding factors.
A wide variety of postnatal contributors to autism have been proposed, including gastrointestinal or immune system abnormalities, allergies, and exposure of children to drugs, infection, certain foods, or heavy metals. The evidence for these risk factors is anecdotal and has not been confirmed by reliable studies.
Paracetamol has been suggested as a possible risk factor for autism. A study has found that male children exposed to Paracetamol before the age of 2 years old are associated with being at risk for being diagnosed with ASD.
This theory hypothesizes that an early developmental failure involving the amygdala cascades on the development of cortical areas that mediate social perception in the visual domain. The fusiform face area of the ventral stream is implicated. The idea is that it is involved in social knowledge and social cognition, and that the deficits in this network are instrumental in causing autism.
This theory hypothesizes that autoantibodies that target the brain or elements of brain metabolism may cause or exacerbate autism. It is related to the maternal infection theory, except that it postulates that the effect is caused by the individual's own antibodies, possibly due to an environmental trigger after birth. It is also related to several other hypothesized causes; for example, viral infection has been hypothesized to cause autism via an autoimmune mechanism.
Interactions between the immune system and the nervous system begin early during embryogenesis, and successful neurodevelopment depends on a balanced immune response. It is possible that aberrant immune activity during critical periods of neurodevelopment is part of the mechanism of some forms of ASD. A small percentage of autism cases are associated with infection, usually before birth. Results from immune studies have been contradictory. Some abnormalities have been found in specific subgroups, and some of these have been replicated. It is not known whether these abnormalities are relevant to the pathology of autism, for example, by infection or autoimmunity, or whether they are secondary to the disease processes. As autoantibodies are found in diseases other than ASD, and are not always present in ASD, the relationship between immune disturbances and autism remains unclear and controversial. A 2015 systematic review and meta-analysis found that children with a family history of autoimmune diseases were at a greater risk of autism compared to children without such a history.
When an underlying maternal autoimmune disease is present, antibodies circulating to the fetus could contribute to the development of autism spectrum disorders.
Gastrointestinal problems are one of the most commonly associated medical disorders in people with autism. These are linked to greater social impairment, irritability, behavior and sleep problems, language impairments and mood changes, so the theory that they are an overlap syndrome has been postulated. Studies indicate that gastrointestinal inflammation, immunoglobulin E-mediated or cell-mediated food allergies, gluten-related disorders (celiac disease, wheat allergy, non-celiac gluten sensitivity), visceral hypersensitivity, dysautonomia and gastroesophageal reflux are the mechanisms that possibly link both.
A 2016 review concludes that enteric nervous system abnormalities might play a role in several neurological disorders, including autism. Neural connections and the immune system are a pathway that may allow diseases originated in the intestine to spread to the brain. A 2018 review suggests that the frequent association of gastrointestinal disorders and autism is due to abnormalities of the gut–brain axis.
The "leaky gut" hypothesis is popular among parents of children with autism. It is based on the idea that defects in the intestinal barrier produce an excessive increase of the intestinal permeability, allowing substances present in the intestine, including bacteria, environmental toxins and food antigens, to pass into the blood. The data supporting this theory are limited and contradictory, since both increased intestinal permeability and normal permeability have been documented in people with autism. Studies with mice provide some support to this theory and suggest the importance of intestinal flora, demonstrating that the normalization of the intestinal barrier was associated with an improvement in some of the ASD-like behaviours. Studies on subgroups of people with ASD showed the presence of high plasma levels of zonulin, a protein that regulates permeability opening the "pores" of the intestinal wall, as well as intestinal dysbiosis (reduced levels of Bifidobacteria and increased abundance of Akkermansia muciniphila, Escherichia coli, Clostridia and Candida fungi) that promotes the production of proinflammatory cytokines, all of which produces excessive intestinal permeability. This allows passage of bacterial endotoxins from the gut into the bloodstream, stimulating liver cells to secrete tumor necrosis factor alpha (TNFα), which modulates blood–brain barrier permeability. Studies on ASD people showed that TNFα cascades produce proinflammatory cytokines, leading to peripheral inflammation and activation of microglia in the brain, which indicates neuroinflammation. In addition, neuroactive opioid peptides from digested foods have been shown to leak into the bloodstream and permeate the blood–brain barrier, influencing neural cells and causing autistic symptoms. (See Endogenous opiate precursor theory)
After a preliminary 1998 study of three children with ASD treated with secretin infusion reported improved GI function and dramatic improvement in behavior, many parents sought secretin treatment and a black market for the hormone developed quickly. Later studies found secretin clearly ineffective in treating autism.
Endogenous opiate precursor theoryEdit
In 1979, Jaak Panksepp proposed a connection between autism and opiates, noting that injections of minute quantities of opiates in young laboratory animals induce symptoms similar to those observed among autistic children. The possibility of a relationship between autism and the consumption of gluten and casein was first articulated by Kalle Reichelt in 1991.
Opiate theory hypothesizes that autism is the result of a metabolic disorder in which opioid peptides gliadorphin (aka gluteomorphin) and casomorphin, produced through metabolism of gluten (present in wheat and related cereals) and casein (present in dairy products), pass through an abnormally permeable intestinal wall and then proceed to exert an effect on neurotransmission through binding with opioid receptors. It has been postulated that the resulting excess of opioids affects brain maturation, and causes autistic symptoms, including behavioural difficulties, attention problems, and alterations in communicative capacity and social and cognitive functioning.
Although high levels of these opioids are eliminated in the urine, it has been suggested that a small part of them cross into the brain causing interference of signal transmission and disruption of normal activity. Three studies have reported that urine samples of people with autism show an increased 24-hour peptide excretion. A study with a control group found no appreciable differences in opioid levels in urine samples of people with autism compared to controls. Two studies showed an increased opioid levels in cerebrospinal fluid of people with autism.
The theory further states that removing opiate precursors from a child's diet may allow time for these behaviors to cease, and neurological development in very young children to resume normally. As of 2014 there is no good evidence that a gluten-free diet is of benefit as a standard treatment for autism. Problems observed in studies carried out include the suspicion that there were transgressions of the diet because the participants asked for food containing gluten or casein to siblings and peers; and the lack of a washout period, that could diminish the effectiveness of the treatment if gluten or casein peptides have a long term residual effect, which is especially relevant in studies of short duration. In the subset of people who have gluten sensitivity there is limited evidence that suggests that a gluten-free diet may improve some autistic behaviors.
Lack of vitamin DEdit
The hypothesis that vitamin D deficiency has a role in autism is biologically plausible, but not researched. Vitamin D deficiency is found more often in children with autism than in children who are considered to be healthy.
Lead poisoning has been suggested as a possible risk factor for autism, as the lead blood levels of autistic children has been reported to be significantly higher than typical. The atypical eating behaviors of autistic children, along with habitual mouthing and pica, make it hard to determine whether increased lead levels are a cause or a consequence of autism.
Locus coeruleus–noradrenergic systemEdit
This theory hypothesizes that autistic behaviors depend at least in part on a developmental dysregulation that results in impaired function of the locus coeruleus–noradrenergic (LC-NA) system. The LC-NA system is heavily involved in arousal and attention; for example, it is related to the brain's acquisition and use of environmental cues.
This theory hypothesizes that autism is associated with mercury poisoning, based on perceived similarity of symptoms and reports of mercury or its biomarkers in some autistic children. This view has gained little traction in the scientific community as the typical symptoms of mercury toxicity are significantly different from symptoms seen in autism. The principal source of human exposure to organic mercury is via fish consumption and for inorganic mercury is dental amalgams. The evidence so far is indirect for the association between autism and mercury exposure after birth, as no direct test has been reported, and there is no evidence of an association between autism and postnatal exposure to any neurotoxicant. A meta-analysis published in 2007 concluded that there was no link between mercury and autism.
This theory hypothesizes that toxicity and oxidative stress may cause autism in some cases. Evidence includes genetic effects on metabolic pathways, reduced antioxidant capacity, enzyme changes, and enhanced biomarkers for oxidative stress; however, the overall evidence is weaker than it is for involvement oxidative stress with disorders such as schizophrenia. One theory is that stress damages Purkinje cells in the cerebellum after birth, and it is possible that glutathione is involved. Autistic children have lower levels of total glutathione, and higher levels of oxidized glutathione. Based on this theory, antioxidants may be a useful treatment for autism.
The social construct theory says that the boundary between normal and abnormal is subjective and arbitrary, so autism does not exist as an objective entity, but only as a social construct. It further argues that autistic individuals themselves have a way of being that is partly socially constructed.
Asperger syndrome and high-functioning autism are particular targets of the theory that social factors determine what it means to be autistic. The theory hypothesizes that individuals with these diagnoses inhabit the identities that have been ascribed to them, and promote their sense of well-being by resisting or appropriating autistic ascriptions.
Lynn Waterhouse suggests that autism has been reified, in that social processes have endowed it with more reality than is justified by the scientific evidence.
Many studies have presented evidence for and against association of autism with viral infection after birth. Laboratory rats infected with Borna disease virus show some symptoms similar to those of autism but blood studies of autistic children show no evidence of infection by this virus. Members of the herpes virus family may have a role in autism, but the evidence so far is anecdotal. Viruses have long been suspected as triggers for immune-mediated diseases such as multiple sclerosis but showing a direct role for viral causation is difficult in those diseases, and mechanisms, whereby viral infections could lead to autism, are speculative.
Bruno Bettelheim believed that autism was linked to early childhood trauma, and his work was highly influential for decades both in the medical and popular spheres. In his discredited theory, he blamed the mothers of individuals with autism for having caused their child's condition through the withholding of affection. Leo Kanner, who first described autism, suggested that parental coldness might contribute to autism. Although Kanner eventually renounced the theory, Bettelheim put an almost exclusive emphasis on it in both his medical and his popular books. Treatments based on these theories failed to help children with autism, and after Bettelheim's death, his reported rates of cure (around 85%) were found to be fraudulent.
Scientific studies have consistently refuted a causal relationship between vaccinations and autism. Despite this, some parents believe that vaccinations cause autism; they therefore delay or avoid immunizing their children (for example, under the "vaccine overload" hypothesis that giving many vaccines at once may overwhelm a child's immune system and lead to autism, even though this hypothesis has no scientific evidence and is biologically implausible). Diseases such as measles can cause severe disabilities and even death, so the risk of death or disability for an unvaccinated child is higher than the risk for a child who has been vaccinated. Despite medical evidence, antivaccine activism continues. A developing tactic is the "promotion of irrelevant research [as] an active aggregation of several questionable or peripherally related research studies in an attempt to justify the science underlying a questionable claim."
The MMR vaccine as a cause of autism is one of the most extensively debated hypotheses regarding the origins of autism. Andrew Wakefield et al. reported a study of 12 children who had autism and bowel symptoms, in some cases reportedly with onset after MMR. Although the paper, which was later retracted by the journal, concluded "We did not prove an association between measles, mumps, and rubella vaccine and the syndrome described," Wakefield nevertheless suggested a false notion during a 1998 press conference that giving children the vaccines in three separate doses would be safer than a single dose. Administering the vaccines in three separate doses does not reduce the chance of adverse effects, and it increases the opportunity for infection by the two diseases not immunized against first.
In 2004, the interpretation of a causal link between MMR vaccine and autism was formally retracted by ten of Wakefield's twelve co-authors. The retraction followed an investigation by The Sunday Times, which stated that Wakefield "acted dishonestly and irresponsibly". The Centers for Disease Control and Prevention, the Institute of Medicine of the National Academy of Sciences, and the U.K. National Health Service have all concluded that there is no evidence of a link between the MMR vaccine and autism.
In February 2010, The Lancet, which published Wakefield's study, fully retracted it after an independent auditor found the study to be flawed. In January 2011, an investigation published in the journal BMJ described the Wakefield study as the result of deliberate fraud and manipulation of data.
Perhaps the best-known hypothesis involving mercury and autism involves the use of the mercury-based compound thiomersal, a preservative that has been phased out from most childhood vaccinations in developed countries including US and the EU. There is no scientific evidence for a causal connection between thiomersal and autism, but parental concern about a relationship between thiomersal and vaccines has led to decreasing rates of childhood immunizations and increasing likelihood of disease outbreaks. In 1999, due to concern about the dose of mercury infants were being exposed to, the U.S. Public Health Service recommended that thiomersal be removed from childhood vaccines, and by 2002 the flu vaccine was the only childhood vaccine containing more than trace amounts of thimerosal. Despite this, autism rates did not decrease after the removal of thimerosal, in the US or other countries that also removed thimerosal from their childhood vaccines.
A causal link between thimerosal and autism has been rejected by international scientific and medical professional bodies including the American Medical Association, the American Academy of Pediatrics, the American College of Medical Toxicology, the Canadian Paediatric Society, the U.S. National Academy of Sciences, the Food and Drug Administration, Centers for Disease Control and Prevention, the World Health Organization, the Public Health Agency of Canada, and the European Medicines Agency.
- Trottier G, Srivastava L, Walker CD (March 1999). "Etiology of infantile autism: a review of recent advances in genetic and neurobiological research". Journal of Psychiatry & Neuroscience (Review). 24 (2): 103–15. PMC 1188990. PMID 10212552.
- "What Is Autism Spectrum Disorder?". www.psychiatry.org. Retrieved 2021-07-30.
- Freitag CM (January 2007). "The genetics of autistic disorders and its clinical relevance: a review of the literature". Molecular Psychiatry (Review). 12 (1): 2–22. doi:10.1038/sj.mp.4001896. PMID 17033636. S2CID 205678822.
- Arndt TL, Stodgell CJ, Rodier PM (2005). "The teratology of autism". International Journal of Developmental Neuroscience (Review). 23 (2–3): 189–99. doi:10.1016/j.ijdevneu.2004.11.001. PMID 15749245. S2CID 17797266.
- Doja A, Roberts W (November 2006). "Immunizations and autism: a review of the literature". The Canadian Journal of Neurological Sciences (Review). 33 (4): 341–6. doi:10.1017/s031716710000528x. PMID 17168158. S2CID 4670282.
- American Psychiatric Association (2000). "Diagnostic criteria for 299.00 Autistic Disorder". Diagnostic and Statistical Manual of Mental Disorders (4th, text revision (DSM-IV-TR) ed.). ISBN 0-89042-025-4.
- World Health Organization (2006). "F84. Pervasive developmental disorders". International Statistical Classification of Diseases and Related Health Problems (10th (ICD-10) ed.). Retrieved 2007-06-25.
- McPartland JC, Law K, Dawson G (August 26, 2015). "Autism Spectrum Disorder". Encyclopedia of Mental Health. Encyclopedia of Mental Health (Second Edition). pp. 124–130. doi:10.1016/B978-0-12-397045-9.00230-5. ISBN 978-0-12-397753-3.
- Happé F, Ronald A (December 2008). "The 'fractionable autism triad': a review of evidence from behavioural, genetic, cognitive and neural research". Neuropsychology Review (Review). 18 (4): 287–304. doi:10.1007/s11065-008-9076-8. PMID 18956240. S2CID 13928876.
- Happé F, Ronald A, Plomin R (October 2006). "Time to give up on a single explanation for autism". Nature Neuroscience (Review). 9 (10): 1218–20. doi:10.1038/nn1770. PMID 17001340. S2CID 18697986.
- Geschwind DH (2009). "Advances in autism". Annual Review of Medicine (Review). 60: 367–80. doi:10.1146/annurev.med.60.053107.121225. PMC 3645857. PMID 19630577.
- Mandy WP, Skuse DH (August 2008). "Research review: What is the association between the social-communication element of autism and repetitive interests, behaviours and activities?". Journal of Child Psychology and Psychiatry, and Allied Disciplines (Review). 49 (8): 795–808. doi:10.1111/j.1469-7610.2008.01911.x. PMID 18564070.
- Newschaffer CJ, Croen LA, Daniels J, Giarelli E, Grether JK, Levy SE, et al. (2007). "The epidemiology of autism spectrum disorders". Annual Review of Public Health (Review). 28: 235–58. doi:10.1146/annurev.publhealth.28.021406.144007. PMID 17367287.
- Christison GW, Ivany K (April 2006). "Elimination diets in autism spectrum disorders: any wheat amidst the chaff?". Journal of Developmental and Behavioral Pediatrics (Review). 27 (2 Suppl): S162-71. doi:10.1097/00004703-200604002-00015. PMID 16685183.
- Saplakoglu Y (8 February 2019). "Measles Outbreak Spurs Vaccination Surge in Anti-Vaxxer Hotspot". Live Science.
- Joseph R (12 February 2019). "Measles vaccinations spike 500% after outbreak hits anti-vaxxer 'hotspot'". Global News.
- Schultz ST (2010). "Does thimerosal or other mercury exposure increase the risk for autism? A review of current literature". Acta Neurobiologiae Experimentalis. 70 (2): 187–95. PMID 20628442.
- Hallmayer J, Cleveland S, Torres A, Phillips J, Cohen B, Torigoe T, et al. (November 2011). "Genetic heritability and shared environmental factors among twin pairs with autism". Archives of General Psychiatry. 68 (11): 1095–102. doi:10.1001/archgenpsychiatry.2011.76. PMC 4440679. PMID 21727249.
- Ronald A, Hoekstra RA (April 2011). "Autism spectrum disorders and autistic traits: a decade of new twin studies". American Journal of Medical Genetics. Part B, Neuropsychiatric Genetics. 156B (3): 255–74. doi:10.1002/ajmg.b.31159. PMID 21438136. S2CID 13196298.
- Folstein SE, Rosen-Sheidley B (December 2001). "Genetics of autism: complex aetiology for a heterogeneous disorder". Nature Reviews. Genetics (Review). 2 (12): 943–55. doi:10.1038/35103559. PMID 11733747. S2CID 9331084.
- Sebat J, Lakshmi B, Malhotra D, Troge J, Lese-Martin C, Walsh T, et al. (April 2007). "Strong association of de novo copy number mutations with autism". Science. 316 (5823): 445–9. Bibcode:2007Sci...316..445S. doi:10.1126/science.1138659. PMC 2993504. PMID 17363630.
- Uher R (December 2009). "The role of genetic variation in the causation of mental illness: an evolution-informed framework". Molecular Psychiatry. 14 (12): 1072–82. doi:10.1038/mp.2009.85. PMID 19704409. S2CID 7623011.
- Hultman CM, Sandin S, Levine SZ, Lichtenstein P, Reichenberg A (December 2011). "Advancing paternal age and risk of autism: new evidence from a population-based study and a meta-analysis of epidemiological studies". Molecular Psychiatry. 16 (12): 1203–12. doi:10.1038/mp.2010.121. PMID 21116277. S2CID 21581363.
- Kong A, Frigge ML, Masson G, Besenbacher S, Sulem P, Magnusson G, et al. (August 2012). "Rate of de novo mutations and the importance of father's age to disease risk". Nature. 488 (7412): 471–5. Bibcode:2012Natur.488..471K. doi:10.1038/nature11396. PMC 3548427. PMID 22914163.
- Hatton DD, Sideris J, Skinner M, Mankowski J, Bailey DB, Roberts J, Mirrett P (September 2006). "Autistic behavior in children with fragile X syndrome: prevalence, stability, and the impact of FMRP". American Journal of Medical Genetics. Part A. 140A (17): 1804–13. doi:10.1002/ajmg.a.31286. PMID 16700053. S2CID 11017841.
- Amir RE, Van den Veyver IB, Wan M, Tran CQ, Francke U, Zoghbi HY (October 1999). "Rett syndrome is caused by mutations in X-linked MECP2, encoding methyl-CpG-binding protein 2". Nature Genetics. 23 (2): 185–8. doi:10.1038/13810. PMID 10508514. S2CID 3350350.
- Sebat J, Lakshmi B, Troge J, Alexander J, Young J, Lundin P, et al. (July 2004). "Large-scale copy number polymorphism in the human genome". Science. 305 (5683): 525–8. Bibcode:2004Sci...305..525S. doi:10.1126/science.1098918. PMID 15273396. S2CID 20357402.
- Iafrate AJ, Feuk L, Rivera MN, Listewnik ML, Donahoe PK, Qi Y, et al. (September 2004). "Detection of large-scale variation in the human genome". Nature Genetics. 36 (9): 949–51. doi:10.1038/ng1416. PMID 15286789. S2CID 1433674.
- Pinto D, Delaby E, Merico D, Barbosa M, Merikangas A, Klei L, et al. (May 2014). "Convergence of genes and cellular pathways dysregulated in autism spectrum disorders". American Journal of Human Genetics. 94 (5): 677–94. doi:10.1016/j.ajhg.2014.03.018. PMC 4067558. PMID 24768552.
- Levy D, Ronemus M, Yamrom B, Lee YH, Leotta A, Kendall J, et al. (June 2011). "Rare de novo and transmitted copy-number variation in autistic spectrum disorders". Neuron. 70 (5): 886–97. doi:10.1016/j.neuron.2011.05.015. PMID 21658582. S2CID 11132936.
- Sanders SJ, Ercan-Sencicek AG, Hus V, Luo R, Murtha MT, Moreno-De-Luca D, et al. (June 2011). "Multiple recurrent de novo CNVs, including duplications of the 7q11.23 Williams syndrome region, are strongly associated with autism". Neuron. 70 (5): 863–85. doi:10.1016/j.neuron.2011.05.002. PMC 3939065. PMID 21658581.
- Brandler WM, Antaki D, Gujral M, Noor A, Rosanio G, Chapman TR, et al. (April 2016). "Frequency and Complexity of De Novo Structural Mutation in Autism". American Journal of Human Genetics. 98 (4): 667–79. doi:10.1016/j.ajhg.2016.02.018. PMC 4833290. PMID 27018473.
- Iossifov I, Ronemus M, Levy D, Wang Z, Hakker I, Rosenbaum J, et al. (April 2012). "De novo gene disruptions in children on the autistic spectrum". Neuron. 74 (2): 285–99. doi:10.1016/j.neuron.2012.04.009. PMC 3619976. PMID 22542183.
- De Rubeis S, He X, Goldberg AP, Poultney CS, Samocha K, Cicek AE, et al. (November 2014). "Synaptic, transcriptional and chromatin genes disrupted in autism". Nature. 515 (7526): 209–15. Bibcode:2014Natur.515..209.. doi:10.1038/nature13772. PMC 4402723. PMID 25363760.
- Iossifov I, O'Roak BJ, Sanders SJ, Ronemus M, Krumm N, Levy D, et al. (November 2014). "The contribution of de novo coding mutations to autism spectrum disorder". Nature. 515 (7526): 216–21. Bibcode:2014Natur.515..216I. doi:10.1038/nature13908. PMC 4313871. PMID 25363768.
- Neale BM, Kou Y, Liu L, Ma'ayan A, Samocha KE, Sabo A, et al. (April 2012). "Patterns and rates of exonic de novo mutations in autism spectrum disorders". Nature. 485 (7397): 242–5. Bibcode:2012Natur.485..242N. doi:10.1038/nature11011. PMC 3613847. PMID 22495311.
- Sanders SJ, Murtha MT, Gupta AR, Murdoch JD, Raubeson MJ, Willsey AJ, et al. (April 2012). "De novo mutations revealed by whole-exome sequencing are strongly associated with autism". Nature. 485 (7397): 237–41. Bibcode:2012Natur.485..237S. doi:10.1038/nature10945. PMC 3667984. PMID 22495306.
- O'Roak BJ, Vives L, Girirajan S, Karakoc E, Krumm N, Coe BP, et al. (April 2012). "Sporadic autism exomes reveal a highly interconnected protein network of de novo mutations". Nature. 485 (7397): 246–50. Bibcode:2012Natur.485..246O. doi:10.1038/nature10989. PMC 3350576. PMID 22495309.
- Ronemus M, Iossifov I, Levy D, Wigler M (February 2014). "The role of de novo mutations in the genetics of autism spectrum disorders". Nature Reviews. Genetics. 15 (2): 133–41. doi:10.1038/nrg3585. PMID 24430941. S2CID 9073763.
- Betancur C (March 2011). "Etiological heterogeneity in autism spectrum disorders: more than 100 genetic and genomic disorders and still counting" (PDF). Brain Research. 1380: 42–77. doi:10.1016/j.brainres.2010.11.078. PMID 21129364. S2CID 41429306.
- "SFARI Gene". SFARI gene. Archived from the original on 2016-04-01. Retrieved 2016-04-13.
- Stefansson H, Meyer-Lindenberg A, Steinberg S, Magnusdottir B, Morgen K, Arnarsdottir S, et al. (January 2014). "CNVs conferring risk of autism or schizophrenia affect cognition in controls". Nature. 505 (7483): 361–6. Bibcode:2014Natur.505..361S. doi:10.1038/nature12818. hdl:2336/311615. PMID 24352232. S2CID 3842341.
- Shinawi M, Liu P, Kang SH, Shen J, Belmont JW, Scott DA, et al. (May 2010). "Recurrent reciprocal 16p11.2 rearrangements associated with global developmental delay, behavioural problems, dysmorphism, epilepsy, and abnormal head size". Journal of Medical Genetics. 47 (5): 332–41. doi:10.1136/jmg.2009.073015. PMC 3158566. PMID 19914906.
- Brandler WM, Sebat J (14 January 2015). "From de novo mutations to personalized therapeutic interventions in autism". Annual Review of Medicine. 66 (1): 487–507. doi:10.1146/annurev-med-091113-024550. PMID 25587659.
- Zaslavsky K, Zhang WB, McCready FP, Rodrigues DC, Deneault E, Loo C, et al. (April 2019). "SHANK2 mutations associated with autism spectrum disorder cause hyperconnectivity of human neurons". Nature Neuroscience. 22 (4): 556–564. doi:10.1038/s41593-019-0365-8. PMC 6475597. PMID 30911184.
- Miyake K, Hirasawa T, Koide T, Kubota T (2012). "Epigenetics in autism and other neurodevelopmental diseases". Advances in Experimental Medicine and Biology (Review). 724: 91–8. doi:10.1007/978-1-4614-0653-2_7. ISBN 978-1-4614-0652-5. PMID 22411236.
- Schanen NC (October 2006). "Epigenetics of autism spectrum disorders". Human Molecular Genetics (Review). 15 Spec No 2: R138-50. doi:10.1093/hmg/ddl213. PMID 16987877.
- Pickles A, Bolton P, Macdonald H, Bailey A, Le Couteur A, Sim CH, Rutter M (September 1995). "Latent-class analysis of recurrence risks for complex phenotypes with selection and measurement error: a twin and family history study of autism". American Journal of Human Genetics. 57 (3): 717–26. PMC 1801262. PMID 7668301.
- Risch N, Spiker D, Lotspeich L, Nouri N, Hinds D, Hallmayer J, et al. (August 1999). "A genomic screen of autism: evidence for a multilocus etiology". American Journal of Human Genetics. 65 (2): 493–507. doi:10.1086/302497. PMC 1377948. PMID 10417292.
- Samaco RC, Hogart A, LaSalle JM (February 2005). "Epigenetic overlap in autism-spectrum neurodevelopmental disorders: MECP2 deficiency causes reduced expression of UBE3A and GABRB3". Human Molecular Genetics. 14 (4): 483–92. doi:10.1093/hmg/ddi045. PMC 1224722. PMID 15615769.
- Jiang YH, Sahoo T, Michaelis RC, Bercovich D, Bressler J, Kashork CD, et al. (November 2004). "A mixed epigenetic/genetic model for oligogenic inheritance of autism with a limited role for UBE3A". American Journal of Medical Genetics. Part A. 131 (1): 1–10. doi:10.1002/ajmg.a.30297. PMID 15389703. S2CID 9570482.
- Lopez-Rangel E, Lewis ME (2006). "Further evidence for pigenetic influence of MECP2 in Rett, autism and Angelman's syndromes". Clinical Genetics. 69 (1): 23–25. doi:10.1111/j.1399-0004.2006.00543c.x. S2CID 85160435.
- Hagerman RJ, Ono MY, Hagerman PJ (September 2005). "Recent advances in fragile X: a model for autism and neurodegeneration". Current Opinion in Psychiatry. 18 (5): 490–6. doi:10.1097/01.yco.0000179485.39520.b0. PMID 16639106. S2CID 33650811.
- Amir RE, Van den Veyver IB, Wan M, Tran CQ, Francke U, Zoghbi HY (October 1999). "Rett syndrome is caused by mutations in X-linked MECP2, encoding methyl-CpG-binding protein 2". Nature Genetics. 23 (2): 185–8. doi:10.1038/13810. PMID 10508514. S2CID 3350350.
- Klose RJ, Bird AP (February 2006). "Genomic DNA methylation: the mark and its mediators". Trends in Biochemical Sciences. 31 (2): 89–97. doi:10.1016/j.tibs.2005.12.008. PMID 16403636.
- Kriaucionis S, Bird A (October 2003). "DNA methylation and Rett syndrome". Human Molecular Genetics. 12 Spec No 2 (2): R221-7. doi:10.1093/hmg/ddg286. PMID 12928486.
- Gardener H, Spiegelman D, Buka SL (July 2009). "Prenatal risk factors for autism: comprehensive meta-analysis". The British Journal of Psychiatry (Review, meta-analysis). 195 (1): 7–14. doi:10.1192/bjp.bp.108.051672. PMC 3712619. PMID 19567888.
- Roullet FI, Lai JK, Foster JA (2013). "In utero exposure to valproic acid and autism--a current review of clinical and animal studies". Neurotoxicology and Teratology (Review). 36: 47–56. doi:10.1016/j.ntt.2013.01.004. PMID 23395807.
- "How pregnancy may shape a child's autism". Spectrum | Autism Research News. 2018-12-05. Retrieved 2021-07-30.
- Libbey JE, Sweeten TL, McMahon WM, Fujinami RS (February 2005). "Autistic disorder and viral infections". Journal of Neurovirology (Review). 11 (1): 1–10. doi:10.1080/13550280590900553. PMID 15804954. S2CID 9962647.
- Mendelsohn NJ, Schaefer GB (March 2008). "Genetic evaluation of autism". Seminars in Pediatric Neurology (Review). 15 (1): 27–31. doi:10.1016/j.spen.2008.01.005. PMID 18342258.
- Meyer U, Yee BK, Feldon J (June 2007). "The neurodevelopmental impact of prenatal infections at different times of pregnancy: the earlier the worse?". The Neuroscientist (Review). 13 (3): 241–56. doi:10.1177/1073858406296401. PMID 17519367. S2CID 26096561.
- Chomiak T, Turner N, Hu B (2013). "What We Have Learned about Autism Spectrum Disorder from Valproic Acid". Pathology Research International (Review). 2013: 712758. doi:10.1155/2013/712758. PMC 3871912. PMID 24381784.
- Avella-Garcia CB, Julvez J, Fortuny J, Rebordosa C, García-Esteban R, Galán IR, et al. (December 2016). "Acetaminophen use in pregnancy and neurodevelopment: attention function and autism spectrum symptoms". International Journal of Epidemiology. 45 (6): 1987–1996. doi:10.1093/ije/dyw115. PMID 27353198.
- Dufour-Rainfray D, Vourc'h P, Tourlet S, Guilloteau D, Chalon S, Andres CR (April 2011). "Fetal exposure to teratogens: evidence of genes involved in autism". Neuroscience and Biobehavioral Reviews (Review). 35 (5): 1254–65. doi:10.1016/j.neubiorev.2010.12.013. PMID 21195109. S2CID 5180756.
- Miller MT, Strömland K, Ventura L, Johansson M, Bandim JM, Gillberg C (2005). "Autism associated with conditions characterized by developmental errors in early embryogenesis: a mini review". International Journal of Developmental Neuroscience. 23 (2–3): 201–19. doi:10.1016/j.ijdevneu.2004.06.007. PMID 15749246. S2CID 14248227.
- Samsam M, Ahangari R, Naser SA (August 2014). "Pathophysiology of autism spectrum disorders: revisiting gastrointestinal involvement and immune imbalance". World Journal of Gastroenterology (Review). 20 (29): 9942–51. doi:10.3748/wjg.v20.i29.9942. PMC 4123375. PMID 25110424.
- Román GC (November 2007). "Autism: transient in utero hypothyroxinemia related to maternal flavonoid ingestion during pregnancy and to other environmental antithyroid agents". Journal of the Neurological Sciences (Review). 262 (1–2): 15–26. doi:10.1016/j.jns.2007.06.023. PMID 17651757. S2CID 31805494.
- Xu G, Jing J, Bowers K, Liu B, Bao W (April 2014). "Maternal diabetes and the risk of autism spectrum disorders in the offspring: a systematic review and meta-analysis". Journal of Autism and Developmental Disorders. 44 (4): 766–75. doi:10.1007/s10803-013-1928-2. PMC 4181720. PMID 24057131.
- Li YM, Ou JJ, Liu L, Zhang D, Zhao JP, Tang SY (January 2016). "Association Between Maternal Obesity and Autism Spectrum Disorder in Offspring: A Meta-analysis". Journal of Autism and Developmental Disorders. 46 (1): 95–102. doi:10.1007/s10803-015-2549-8. PMID 26254893. S2CID 26406333.
- Vohr BR, Poggi Davis E, Wanke CA, Krebs NF (April 2017). "Neurodevelopment: The Impact of Nutrition and Inflammation During Preconception and Pregnancy in Low-Resource Settings". Pediatrics (Review). 139 (Suppl 1): S38–S49. doi:10.1542/peds.2016-2828F. PMID 28562247. S2CID 28637473.
- Lyall K, Schmidt RJ, Hertz-Picciotto I (April 2014). "Maternal lifestyle and environmental risk factors for autism spectrum disorders". International Journal of Epidemiology. 43 (2): 443–64. doi:10.1093/ije/dyt282. PMC 3997376. PMID 24518932.
- Kinney DK, Munir KM, Crowley DJ, Miller AM (October 2008). "Prenatal stress and risk for autism". Neuroscience and Biobehavioral Reviews (Review). 32 (8): 1519–32. doi:10.1016/j.neubiorev.2008.06.004. PMC 2632594. PMID 18598714.
- Rai D, Golding J, Magnusson C, Steer C, Lewis G, Dalman C (2012). "Prenatal and early life exposure to stressful life events and risk of autism spectrum disorders: population-based studies in Sweden and England". PLOS ONE. 7 (6): e38893. Bibcode:2012PLoSO...738893R. doi:10.1371/journal.pone.0038893. PMC 3374800. PMID 22719977.
- Fetal testosterone and autistic traits:
- Auyeung B, Baron-Cohen S (2009). "A role for fetal testosterone in human sex differences". In Zimmerman AW (ed.). Autism: Current Theories and Evidence. Humana. pp. 185–208. doi:10.1007/978-1-60327-489-0_8. ISBN 978-1-60327-488-3.
- Manson JE (October 2008). "Prenatal exposure to sex steroid hormones and behavioral/cognitive outcomes". Metabolism (Review). 57 Suppl 2 (Suppl 2): S16-21. doi:10.1016/j.metabol.2008.07.010. PMID 18803959.
- Abramowicz JS (August 2012). "Ultrasound and autism: association, link, or coincidence?". Journal of Ultrasound in Medicine (Review). 31 (8): 1261–9. doi:10.7863/jum.2012.31.8.1261. PMID 22837291. S2CID 36234852.
- Man KK, Tong HH, Wong LY, Chan EW, Simonoff E, Wong IC (February 2015). "Exposure to selective serotonin reuptake inhibitors during pregnancy and risk of autism spectrum disorder in children: a systematic review and meta-analysis of observational studies". Neuroscience and Biobehavioral Reviews. 49: 82–9. doi:10.1016/j.neubiorev.2014.11.020. hdl:10722/207262. PMID 25498856. S2CID 8862487.
- Brown HK, Hussain-Shamsy N, Lunsky Y, Dennis CE, Vigod SN (January 2017). "The Association Between Antenatal Exposure to Selective Serotonin Reuptake Inhibitors and Autism: A Systematic Review and Meta-Analysis". The Journal of Clinical Psychiatry. 78 (1): e48–e58. doi:10.4088/JCP.15r10194. PMID 28129495.
- Kolevzon A, Gross R, Reichenberg A (April 2007). "Prenatal and perinatal risk factors for autism: a review and integration of findings". Archives of Pediatrics & Adolescent Medicine (Review). 161 (4): 326–33. doi:10.1001/archpedi.161.4.326. PMID 17404128.
- Weisskopf MG, Kioumourtzoglou MA, Roberts AL (December 2015). "Air Pollution and Autism Spectrum Disorders: Causal or Confounded?". Current Environmental Health Reports. 2 (4): 430–9. doi:10.1007/s40572-015-0073-9. PMC 4737505. PMID 26399256.
- Flores-Pajot MC, Ofner M, Do MT, Lavigne E, Villeneuve PJ (November 2016). "Childhood autism spectrum disorders and exposure to nitrogen dioxide, and particulate matter air pollution: A review and meta-analysis". Environmental Research. 151: 763–776. Bibcode:2016ER....151..763F. doi:10.1016/j.envres.2016.07.030. PMID 27609410.
- Rutter M (January 2005). "Incidence of autism spectrum disorders: changes over time and their meaning". Acta Paediatrica (Review). 94 (1): 2–15. doi:10.1111/j.1651-2227.2005.tb01779.x. PMID 15858952. S2CID 79259285.
- Bittker SS, Bell KR (January 2020). "Postnatal Acetaminophen and Potential Risk of Autism Spectrum Disorder among Males". Behavioral Sciences. 10 (1): 26. doi:10.3390/bs10010026. PMC 7017213. PMID 31906400.
- Bittker, Seth S.; Bell, Kathleen R. (2020-01-01). "Postnatal Acetaminophen and Potential Risk of Autism Spectrum Disorder among Males". Behavioral Sciences. 10 (1): 26. doi:10.3390/bs10010026. ISSN 2076-328X. PMC 7017213. PMID 31906400.
- Schultz RT (2005). "Developmental deficits in social perception in autism: the role of the amygdala and fusiform face area". International Journal of Developmental Neuroscience (Review). 23 (2–3): 125–41. doi:10.1016/j.ijdevneu.2004.12.012. PMID 15749240. S2CID 17078137.
- Ashwood P, Van de Water J (November 2004). "Is autism an autoimmune disease?". Autoimmunity Reviews (Review). 3 (7–8): 557–62. doi:10.1016/j.autrev.2004.07.036. PMID 15546805.
- Ashwood P, Wills S, Van de Water J (July 2006). "The immune response in autism: a new frontier for autism research". Journal of Leukocyte Biology (Review). 80 (1): 1–15. doi:10.1189/jlb.1205707. PMID 16698940. S2CID 17531542.
- Stigler KA, Sweeten TL, Posey DJ, McDougle CJ (2009). "Autism and immune factors: a comprehensive review". Res Autism Spectr Disord (Review). 3 (4): 840–860. doi:10.1016/j.rasd.2009.01.007.
- Wills S, Cabanlit M, Bennett J, Ashwood P, Amaral D, Van de Water J (June 2007). "Autoantibodies in autism spectrum disorders (ASD)". Annals of the New York Academy of Sciences (Review). 1107 (1): 79–91. Bibcode:2007NYASA1107...79W. doi:10.1196/annals.1381.009. PMID 17804535. S2CID 24708891.
- Schmitz C, Rezaie P (February 2008). "The neuropathology of autism: where do we stand?". Neuropathology and Applied Neurobiology (Review). 34 (1): 4–11. doi:10.1111/j.1365-2990.2007.00872.x. PMID 17971078. S2CID 23551620.
- Wu S, Ding Y, Wu F, Li R, Xie G, Hou J, Mao P (August 2015). "Family history of autoimmune diseases is associated with an increased risk of autism in children: A systematic review and meta-analysis". Neuroscience and Biobehavioral Reviews. 55: 322–32. doi:10.1016/j.neubiorev.2015.05.004. PMID 25981892. S2CID 42029820.
- Fox E, Amaral D, Van de Water J (October 2012). "Maternal and fetal antibrain antibodies in development and disease". Developmental Neurobiology (Review). 72 (10): 1327–34. doi:10.1002/dneu.22052. PMC 3478666. PMID 22911883.
- Israelyan N, Margolis KG (June 2018). "Serotonin as a link between the gut-brain-microbiome axis in autism spectrum disorders". Pharmacological Research (Review). 132: 1–6. doi:10.1016/j.phrs.2018.03.020. PMC 6368356. PMID 29614380.
- Wasilewska J, Klukowski M (2015). "Gastrointestinal symptoms and autism spectrum disorder: links and risks - a possible new overlap syndrome". Pediatric Health, Medicine and Therapeutics (Review). 6: 153–166. doi:10.2147/PHMT.S85717. PMC 5683266. PMID 29388597.
- Rao M, Gershon MD (September 2016). "The bowel and beyond: the enteric nervous system in neurological disorders". Nature Reviews. Gastroenterology & Hepatology (Review). 13 (9): 517–28. doi:10.1038/nrgastro.2016.107. PMC 5005185. PMID 27435372.
- Azhari A, Azizan F, Esposito G (July 2019). "A systematic review of gut-immune-brain mechanisms in Autism Spectrum Disorder". Developmental Psychobiology (Systematic Review). 61 (5): 752–771. doi:10.1002/dev.21803. PMID 30523646.
- Johnson TW (2006). "Dietary considerations in autism: identifying a reasonable approach". Top Clin Nutr. 21 (3): 212–225. doi:10.1097/00008486-200607000-00008. S2CID 76326593.
- Krishnaswami S, McPheeters ML, Veenstra-Vanderweele J (May 2011). "A systematic review of secretin for children with autism spectrum disorders". Pediatrics (Review). 127 (5): e1322-5. doi:10.1542/peds.2011-0428. PMC 3387870. PMID 21464196.
- Panksepp J (1979). "A neurochemical theory of autism". Trends in Neurosciences. 2: 174–177. doi:10.1016/0166-2236(79)90071-7. S2CID 54373822.
- Millward C, Ferriter M, Calver S, Connell-Jones G (April 2008). "Gluten- and casein-free diets for autistic spectrum disorder". The Cochrane Database of Systematic Reviews (Review) (2): CD003498. doi:10.1002/14651858.CD003498.pub3. PMC 4164915. PMID 18425890.
- Shattock P, Whiteley P (April 2002). "Biochemical aspects in autism spectrum disorders: updating the opioid-excess theory and presenting new opportunities for biomedical intervention". Expert Opinion on Therapeutic Targets (Review). 6 (2): 175–83. doi:10.1517/14728184.108.40.206. PMID 12223079. S2CID 40904799.
- Christison GW, Ivany K (April 2006). "Elimination diets in autism spectrum disorders: any wheat amidst the chaff?". Journal of Developmental and Behavioral Pediatrics. 27 (2 Suppl): S162-71. doi:10.1097/00004703-200604002-00015. PMID 16685183.
- Buie T (May 2013). "The relationship of autism and gluten". Clinical Therapeutics (Review). 35 (5): 578–83. doi:10.1016/j.clinthera.2013.04.011. PMID 23688532.
At this time, the studies attempting to treat symptoms of autism with diet have not been sufficient to support the general institution of a gluten-free or other diet for all children with autism.
- Marí-Bauset S, Zazpe I, Mari-Sanchis A, Llopis-González A, Morales-Suárez-Varela M (December 2014). "Evidence of the gluten-free and casein-free diet in autism spectrum disorders: a systematic review". Journal of Child Neurology. 29 (12): 1718–27. doi:10.1177/0883073814531330. hdl:10171/37087. PMID 24789114. S2CID 19874518.
- Millward C, Ferriter M, Calver S, Connell-Jones G (April 2008). Ferriter M (ed.). "Gluten- and casein-free diets for autistic spectrum disorder". The Cochrane Database of Systematic Reviews (2): CD003498. doi:10.1002/14651858.CD003498.pub3. PMC 4164915. PMID 18425890.
- Volta U, Caio G, De Giorgio R, Henriksen C, Skodje G, Lundin KE (June 2015). "Non-celiac gluten sensitivity: a work-in-progress entity in the spectrum of wheat-related disorders". Best Practice & Research. Clinical Gastroenterology. 29 (3): 477–91. doi:10.1016/j.bpg.2015.04.006. PMID 26060112.
autism spectrum disorders (ASD) have been hypothesized to be associated with NCGS [47,48]. Notably, a gluten- and casein-free diet might have a positive effect in improving hyperactivity and mental confusion in some patients with ASD. This very exciting association between NCGS and ASD deserves further study before conclusions can be firmly drawn
- San Mauro Martín I, Garicano Vilar E, Collado Yurrutia L, Ciudad Cabañas MJ (December 2014). "[Is gluten the great etiopathogenic agent of disease in the XXI century?]" [Is gluten the great etiopathogenic agent of disease in the XXI century?]. Nutricion Hospitalaria (in Spanish). 30 (6): 1203–10. doi:10.3305/nh.2014.30.6.7866. PMID 25433099.
- Kočovská E, Fernell E, Billstedt E, Minnis H, Gillberg C (2012). "Vitamin D and autism: clinical review" (PDF). Research in Developmental Disabilities (Review). 33 (5): 1541–50. doi:10.1016/j.ridd.2012.02.015. PMID 22522213.
- Bener, Abdulbari; Khattab, Azhar O.; Al-Dabbagh, Mohamad M. (2014). "Is high prevalence of Vitamin D deficiency evidence for autism disorder?: In a highly endogamous population". Journal of Pediatric Neurosciences. 9 (3): 227–233. doi:10.4103/1817-1745.147574. ISSN 1817-1745. PMC 4302541. PMID 25624924.
- Zafeiriou DI, Ververi A, Vargiami E (June 2007). "Childhood autism and associated comorbidities". Brain & Development (Review). 29 (5): 257–72. doi:10.1016/j.braindev.2006.09.003. PMID 17084999. S2CID 16386209.
- Mehler MF, Purpura DP (March 2009). "Autism, fever, epigenetics and the locus coeruleus". Brain Research Reviews (Review). 59 (2): 388–92. doi:10.1016/j.brainresrev.2008.11.001. PMC 2668953. PMID 19059284. Lay summary – TIME (2009-04-07).
- Austin D (2008). "An epidemiological analysis of the 'autism as mercury poisoning' hypothesis". Int J Risk Saf Med. 20 (3): 135–142. doi:10.3233/JRS-2008-0436.
- Nelson KB, Bauman ML (March 2003). "Thimerosal and autism?". Pediatrics (Review). 111 (3): 674–9. doi:10.1542/peds.111.3.674. PMID 12612255.
- Davidson PW, Myers GJ, Weiss B (April 2004). "Mercury exposure and child development outcomes". Pediatrics (Review, historical article). 113 (4 Suppl): 1023–9. PMID 15060195.
- Ng DK, Chan CH, Soo MT, Lee RS (February 2007). "Low-level chronic mercury exposure in children and adolescents: meta-analysis". Pediatrics International (Meta-analysis). 49 (1): 80–7. doi:10.1111/j.1442-200X.2007.02303.x. PMID 17250511. S2CID 24367277.
- Ng F, Berk M, Dean O, Bush AI (September 2008). "Oxidative stress in psychiatric disorders: evidence base and therapeutic implications". The International Journal of Neuropsychopharmacology (Review). 11 (6): 851–76. doi:10.1017/S1461145707008401. PMID 18205981.
- Kern JK, Jones AM (2006). "Evidence of toxicity, oxidative stress, and neuronal insult in autism". Journal of Toxicology and Environmental Health Part B: Critical Reviews (Review). 9 (6): 485–99. doi:10.1080/10937400600882079. PMID 17090484. S2CID 1096750.
- Ghanizadeh A, Akhondzadeh S, Hormozi M, Makarem A, Abotorabi-Zarchi M, Firoozabadi A (2012). "Glutathione-related factors and oxidative stress in autism, a review". Current Medicinal Chemistry (Review). 19 (23): 4000–5. doi:10.2174/092986712802002572. PMID 22708999.
- Villagonzalo KA, Dodd S, Dean O, Gray K, Tonge B, Berk M (December 2010). "Oxidative pathways as a drug target for the treatment of autism". Expert Opinion on Therapeutic Targets (Review). 14 (12): 1301–10. doi:10.1517/14728222.2010.528394. PMID 20954799. S2CID 44864562.
- Hacking I (1999). The Social Construction of What?. Harvard University Press. pp. 114–123. ISBN 0-674-00412-4.
- Nadesan MH (2005). "The dialectics of autism: theorizing autism, performing autism, remediating autism, and resisting autism". Constructing Autism: Unravelling the 'Truth' and Understanding the Social. Routledge. pp. 179–213. ISBN 0-415-32181-6.
- Waterhouse L (2013). Rethinking Autism: Variation and Complexity. Academic Press. p. 24. ISBN 978-0-12-415961-7.
Although autism spectrum disorder has not been proven to exist either as a set of meaningful subgroups, or as the expression of a unifying deficit or causal pattern, nonetheless, autism appears to have been unified as a real entity in public opinion... Some researchers have argued that, over time, autism has been transformed from a hypothesis to an assumed reality. This transformation is called reification. Reification is the conversion of a theorized entity into something assumed and believed to be real... the intense public discussion of autism, the long history of autism in the diagnostic manuals of the American Psychiatric Association, and the long history of autism research are in full view, and they all have made autism seem more concrete and less hypothetical.
- Bettelheim B (1967). The Empty Fortress: Infantile Autism and the Birth of the Self. Free Press. ISBN 0-02-903140-0.
- Kanner L (1943). "Autistic disturbances of affective contact". Nerv Child. 2: 217–250. Reprinted in Kanner L (1968). "Autistic disturbances of affective contact". Acta Paedopsychiatrica. 35 (4): 100–36. PMID 4880460.
- Kanner L (July 1949). "Problems of nosology and psychodynamics of early infantile autism". The American Journal of Orthopsychiatry. 19 (3): 416–26. doi:10.1111/j.1939-0025.1949.tb05441.x. PMID 18146742.
- Gardner M (2000). "The brutality of Dr. Bettelheim". Skeptical Inquirer. 24 (6): 12–14.
- Fombonne E, Zakarian R, Bennett A, Meng L, McLean-Heywood D (July 2006). "Pervasive developmental disorders in Montreal, Quebec, Canada: prevalence and links with immunizations". Pediatrics. 118 (1): e139-50. doi:10.1542/peds.2005-2993. PMID 16818529. S2CID 17981294.
- Gross L (May 2009). "A broken trust: lessons from the vaccine--autism wars". PLOS Biology. 7 (5): e1000114. doi:10.1371/journal.pbio.1000114. PMC 2682483. PMID 19478850.
- Taylor LE, Swerdfeger AL, Eslick GD (June 2014). "Vaccines are not associated with autism: an evidence-based meta-analysis of case-control and cohort studies". Vaccine. 32 (29): 3623–9. doi:10.1016/j.vaccine.2014.04.085. PMID 24814559.
- Hilton S, Petticrew M, Hunt K (May 2006). "'Combined vaccines are like a sudden onslaught to the body's immune system': parental concerns about vaccine 'overload' and 'immune-vulnerability'". Vaccine. 24 (20): 4321–7. doi:10.1016/j.vaccine.2006.03.003. PMID 16581162.
- Gerber JS, Offit PA (February 2009). "Vaccines and autism: a tale of shifting hypotheses". Clinical Infectious Diseases (Review). 48 (4): 456–61. doi:10.1086/596476. PMC 2908388. PMID 19128068. Archived from the original on 2011-08-12. Retrieved 2009-05-06. Lay summary – IDSA (2009-01-30).
- Paul R (June 2009). "Parents ask: Am I risking autism if I vaccinate my children?". Journal of Autism and Developmental Disorders. 39 (6): 962–3. doi:10.1007/s10803-009-0739-y. PMID 19363650. S2CID 34467853.
- Foster CA, Ortiz SM (2017). "Vaccines, Autism, and the Promotion of Irrelevant Research: A Science-Pseudoscience Analysis". Skeptical Inquirer. 41 (3): 44–48. Archived from the original on 2018-10-06. Retrieved 6 October 2018.
- The Editors Of The Lancet (February 2010). "Retraction--Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children". Lancet. 375 (9713): 445. doi:10.1016/S0140-6736(10)60175-4. PMID 20137807. S2CID 26364726. Lay summary – BBC News (2010-02-02).
- Wakefield AJ, Murch SH, Anthony A, Linnell J, Casson DM, Malik M, et al. (February 1998). "Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children". Lancet. 351 (9103): 637–41. doi:10.1016/S0140-6736(97)11096-0. PMID 9500320. S2CID 439791. (Retracted, see doi:10.1016/S0140-6736(10)60175-7)
- National Health Service (2004). "MMR: myths and truths". Archived from the original on 2008-09-13. Retrieved 2007-09-03.
- MMR vs three separate vaccines:
- Halsey NA; Hyman SL; Conference Writing Panel (2001). "Measles-mumps-rubella vaccine and autistic spectrum disorder: report from the New Challenges in Childhood Immunizations Conference convened in Oak Brook, Illinois, June 12–13, 2000". Pediatrics. 107 (5): e84. doi:10.1542/peds.107.5.e84. PMID 11331734.
- Leitch R, Halsey N, Hyman SL (2002). "MMR—Separate administration-has it been done?". Pediatrics. 109 (1): 172. doi:10.1542/peds.109.1.172. PMID 11773568.
- Miller E (2002). "MMR vaccine: review of benefits and risks". J Infect. 44 (1): 1–6. doi:10.1053/jinf.2001.0930. PMID 11972410.
- Murch SH, Anthony A, Casson DH, Malik M, Berelowitz M, Dhillon AP, et al. (March 2004). "Retraction of an interpretation". Lancet. 363 (9411): 750. doi:10.1016/S0140-6736(04)15715-2. PMID 15016483. S2CID 5128036.
- Deer B (2008-11-02). "The MMR-autism crisis – our story so far". Retrieved 2008-12-06.
- "Measles, mumps, and rubella (MMR) vaccine". Centers for Disease Control and Prevention. 2008-12-23. Retrieved 2009-02-14.
- "Immunization safety review: vaccines and autism". Institute of Medicine, National Academy of Sciences. 2004. Archived from the original on 2007-06-23. Retrieved 2007-06-13.
- "MMR the facts". National Health Service. Archived from the original on 2007-06-15. Retrieved 2007-06-13.
- Godlee F, Smith J, Marcovitch H (January 2011). "Wakefield's article linking MMR vaccine and autism was fraudulent". BMJ. 342: c7452. doi:10.1136/bmj.c7452. PMID 21209060. S2CID 43640126.
- Deer B (January 2011). "How the case against the MMR vaccine was fixed". BMJ. 342: c5347. doi:10.1136/bmj.c5347. PMID 21209059. S2CID 46683674.
- "Study linking vaccine to autism was fraud". NPR. Associated Press. 2011-01-05. Archived from the original on 2011-01-07. Retrieved 2011-01-06.
- "Retracted autism study an 'elaborate fraud,' British journal finds". Atlanta. 2011-01-06. Retrieved 2011-01-06.
- "Vaccines, blood and biologics: thimerosal in vaccines". US Food and Drug Administration. 2012. Retrieved October 24, 2013.
- Eaton L (February 2009). "Measles cases in England and Wales rise sharply in 2008". BMJ. 338: b533. doi:10.1136/bmj.b533. PMID 19208716. S2CID 27118639.
- Choi YH, Gay N, Fraser G, Ramsay M (September 2008). "The potential for measles transmission in England". BMC Public Health. 8: 338. doi:10.1186/1471-2458-8-338. PMC 2563003. PMID 18822142.
- Gorski D (7 January 2008). "Mercury in vaccines as a cause of autism and autism spectrum disorders (ASDs): A failed hypothesis". Science-Based Medicine.
- American Medical Association (2004-05-18). "AMA Welcomes New IOM Report Rejecting Link Between Vaccines and Autism". Retrieved 2007-07-23.
- American Academy of Pediatrics (2004-05-18). "What Parents Should Know About Thimerosal". Archived from the original on 2007-07-08. Retrieved 2007-07-23.
- Kurt TL (December 2006). "ACMT position statement: the Iom report on thimerosal and autism" (PDF). Journal of Medical Toxicology. 2 (4): 170–1. doi:10.1007/BF03161188. PMC 3550071. PMID 18072140. Archived from the original (PDF) on 2008-02-29.
- Infectious Diseases and Immunization Committee, Canadian Paediatric Society (2007). "Autistic spectrum disorder: No causal relationship with vaccines". Paediatr Child Health. 12 (5): 393–395. PMC 2528717. PMID 19030398. Archived from the original on 2008-12-02. Retrieved 2008-10-17. Also published (2007) in "Autistic spectrum disorder: No causal relationship with vaccines". The Canadian Journal of Infectious Diseases & Medical Microbiology. 18 (3): 177–9. May 2007. doi:10.1155/2007/267957. PMC 2533550. PMID 18923720..
- "Thimerosal in vaccines". Center for Biologics Evaluation and Research, U.S. Food and Drug Administration. 2007-09-06. Retrieved 2007-10-01.
- World Health Organization (2006). "Questions and answers about autism spectrum disorders (ASD)". Retrieved 2014-11-02.
- National Advisory Committee on Immunization (July 2007). "Thimerosal: updated statement. An Advisory Committee Statement (ACS)". Canada Communicable Disease Report. 33 (ACS-6): 1–13. PMID 17663033.
- European Medicines Agency (2004-03-24). "EMEA Public Statement on Thiomersal in Vaccines for Human Use" (PDF). Archived from the original (PDF) on 2007-06-10. Retrieved 2007-07-22.