Hypoactive sexual desire disorder
Hypoactive sexual desire disorder (HSDD) or inhibited sexual desire (ISD) is considered a sexual dysfunction and is characterized as a lack or absence of sexual fantasies and desire for sexual activity, as judged by a clinician. For this to be regarded as a disorder, it must cause marked distress or interpersonal difficulties and not be better accounted for by another mental disorder, a drug (legal or illegal), or some other medical condition. A person with ISD will not start, or respond to their partner's desire for, sexual activity. HSDD affects approximately 10% of all pre-menopausal women in the United States, or about 6 million women.
|Hypoactive sexual desire disorder|
There are various subtypes. HSDD can be general (general lack of sexual desire) or situational (still has sexual desire, but lacks sexual desire for current partner), and it can be acquired (HSDD started after a period of normal sexual functioning) or lifelong (the person has always had no/low sexual desire.)
HSDD has garnered much criticism, primarily by asexual activists. They argue that HSDD puts asexuality in the same position homosexuality was from 1974 to 1987. The DSM at that time recognised 'ego-dystonic homosexuality' as a disorder, defined as sexual interest in the same sex that caused significant distress. The DSM itself officially recognized this as unnecessarily pathologizing homosexuality and removed it as a disorder in 1987.
In the DSM-5, HSDD was split into male hypoactive sexual desire disorder and female sexual interest/arousal disorder. It was first included in the DSM-III under the name inhibited sexual desire disorder, but the name was changed in the DSM-III-R. Other terms used to describe the phenomenon include sexual aversion and sexual apathy. More informal or colloquial terms are frigidity and frigidness.
Low sexual desire alone is not equivalent to HSDD because of the requirement in HSDD that the low sexual desire causes marked distress and interpersonal difficulty and because of the requirement that the low desire is not better accounted for by another disorder in the DSM or by a general medical problem. It is therefore difficult to say exactly what causes HSDD. It is easier to describe, instead, some of the causes of low sexual desire.
In men, though there are theoretically more types of HSDD/low sexual desire, typically men are only diagnosed with one of three subtypes.
- Lifelong/generalised: The man has little or no desire for sexual stimulation (with a partner or alone) and never had.
- Acquired/generalised: The man previously had sexual interest in his present partner, but lacks interest in sexual activity, partnered or solitary.
- Acquired/situational: The man was previously sexually interested in his present partner but now lacks sexual interest in this partner but has desire for sexual stimulation (i.e. alone or with someone other than his present partner.)
Though it can sometimes be difficult to distinguish between these types, they do not necessarily have the same cause. The cause of lifelong/generalized HSDD is unknown. In the case of acquired/generalized low sexual desire, possible causes include various medical/health problems, psychiatric problems, low levels of testosterone or high levels of prolactin. One theory suggests that sexual desire is controlled by a balance between inhibitory and excitatory factors. This is thought to be expressed via neurotransmitters in selective brain areas. A decrease in sexual desire may therefore be due to an imbalance between neurotransmitters with excitatory activity like dopamine and norepinephrine and neurotransmitters with inhibitory activity, like serotonin. Low sexual desire can also be a side effect of various medications. In the case of acquired/situational HSDD, possible causes include intimacy difficulty, relationship problems, sexual addiction, and chronic illness of the man's partner. The evidence for these is somewhat in question. Some claimed causes of low sexual desire are based on empirical evidence. However, some are based merely on clinical observation. In many cases, the cause of HSDD is simply unknown.
There are some factors that are believed to be possible causes of HSDD in women. As with men, various medical problems, psychiatric problems (such as mood disorders), or increased amounts of prolactin can cause HSDD. Other hormones are believed to be involved as well. Additionally, factors such as relationship problems or stress are believed to be possible causes of reduced sexual desire in women. According to one recent study examining the affective responses and attentional capture of sexual stimuli in women with and without HSDD, women with HSDD do not appear to have a negative association to sexual stimuli, but rather a weaker positive association than women without HSDD.
In the DSM-5, male hypoactive sexual desire disorder is characterized by "persistently or recurrently deficient (or absent) sexual/erotic thoughts or fantasies and desire for sexual activity", as judged by a clinician with consideration for the patient's age and cultural context. Female sexual interest/arousal disorder is defined as a "lack of, or significantly reduced, sexual interest/arousal", manifesting as at least three of the following symptoms: no or little interest in sexual activity, no or few sexual thoughts, no or few attempts to initiate sexual activity or respond to partner's initiation, no or little sexual pleasure/excitement in 75–100% of sexual experiences, no or little sexual interest in internal or external erotic stimuli, and no or few genital/nongenital sensations in 75–100% of sexual experiences.
For both diagnoses, symptoms must persist for at least six months, cause clinically significant distress, and not be better explained by another condition. Simply having lower desire than one's partner is not sufficient for a diagnosis. Self-identification of a lifelong lack of sexual desire as asexuality precludes diagnosis.
HSDD, like many sexual dysfunctions, is something that people are treated for in the context of a relationship. Theoretically, one could be diagnosed with, and treated for, HSDD without being in a relationship. However, relationship status is the most predictive factor accounting for distress in women with low desire and distress is required for a diagnosis of HSDD. Therefore, it is common for both partners to be involved in therapy. Typically, the therapist tries to find a psychological or biological cause of the HSDD. If the HSDD is organically caused, the clinician may try to treat it. If the clinician believes it is rooted in a psychological problem, they may recommend therapy. If not, treatment generally focuses more on relationship and communication issues, improved communication (verbal and nonverbal), working on non-sexual intimacy, or education about sexuality may all be possible parts of treatment. Sometimes problems occur because people have unrealistic perceptions about what normal sexuality is and are concerned that they do not compare well to that, and this is one reason why education can be important. If the clinician thinks that part of the problem is a result of stress, techniques may be recommended to more effectively deal with that. Also, it can be important to understand why the low level of sexual desire is a problem for the relationship because the two partners may associate different meanings with sex but not know it.
In the case of men, the therapy may depend on the subtype of HSDD. Increasing the level of sexual desire of a man with lifelong/generalized HSDD is unlikely. Instead the focus may be on helping the couple to adapt. In the case of acquired/generalized, it is likely that there is some biological reason for it and the clinician may attempt to deal with that. In the case of acquired/situational, some form of psychotherapy may be used, possibly with the man alone and possibly together with his partner.
Flibanserin was the first medication approved by FDA for the treatment of HSDD in pre-menopausal women. Its approval was controversial and a systematic review found its benefits to be marginal. The only other medication approved in the USA for HSDD in pre-menopausal women is bremelanotide, in 2019.
A few studies suggest that the antidepressant, bupropion, can improve sexual function in women who are not depressed, if they have HSDD. The same is true for the anxiolytic, buspirone, which is a 5-HT1A receptor agonist similarly to flibanserin.
The term "frigid" to describe sexual dysfunction derives from medieval and early modern canonical texts about witchcraft. It was thought that witches could put spells on men to make them incapable of erections. Only in the early nineteenth century were women first described as "frigid", and a vast literature exists on what was considered a serious problem if a women did not desire sex with her husband. Many medical texts between 1800-1930 focused on women's frigidity, considering it a sexual pathology.
The French psychoanalyst, Princess Marie Bonaparte, theorized about frigidity and considered herself to suffer from it. In the early versions of the DSM, there were only two sexual dysfunctions listed: frigidity (for women) and impotence (for men).
In 1970, Masters and Johnson published their book Human Sexual Inadequacy describing sexual dysfunctions, though these included only dysfunctions dealing with the function of genitals such as premature ejaculation and impotence for men, and anorgasmia and vaginismus for women. Prior to Masters and Johnson's research, female orgasm was assumed by some to originate primarily from vaginal, rather than clitoral, stimulation. Consequently, feminists have argued that "frigidity" was "defined by men as the failure of women to have vaginal orgasms".
Following this book, sex therapy increased throughout the 1970s. Reports from sex-therapists about people with low sexual desire are reported from at least 1972, but labeling this as a specific disorder did not occur until 1977. In that year, sex therapists Helen Singer Kaplan and Harold Lief independently of each other proposed creating a specific category for people with low or no sexual desire. Lief named it "inhibited sexual desire", and Kaplan named it "hypoactive sexual desire". The primary motivation for this was that previous models for sex therapy assumed certain levels of sexual interest in one's partner and that problems were only caused by abnormal functioning/non-functioning of the genitals or performance anxiety but that therapies based on those problems were ineffective for people who did not sexually desire their partner. The following year, 1978, Lief and Kaplan together made a proposal to the APA's taskforce for sexual disorders for the DSM III, of which Kaplan and Lief were both members. The diagnosis of Inhibited Sexual Desire (ISD) was added to the DSM when the 3rd edition was published in 1980.
For understanding this diagnosis, it is important to recognize the social context in which it was created. In some cultures, low sexual desire may be considered normal and high sexual desire is problematic. For example, sexual desire may be lower in East Asian populations than Euro-Canadian/American populations. In other cultures, this may be reversed. Some cultures try hard to restrain sexual desire. Others try to excite it. Concepts of "normal" levels of sexual desire are culturally dependent and rarely value-neutral. In the 1970s, there were strong cultural messages that sex is good for you and "the more the better". Within this context, people who were habitually uninterested in sex, who in previous times may not have seen this as a problem, were more likely to feel that this was a situation that needed to be fixed. They may have felt alienated by dominant messages about sexuality and increasingly people went to sex-therapists complaining of low sexual desire. It was within this context that the diagnosis of ISD was created.
In the revision of the DSM-III, published in 1987 (DSM-III-R), ISD was subdivided into two categories: Hypoactive Sexual Desire Disorder and Sexual Aversion Disorder (SAD). The former is a lack of interest in sex and the latter is a phobic aversion to sex. In addition to this subdivision, one reason for the change is that the committee involved in revising the psychosexual disorders for the DSM-III-R thought that term "inhibited" suggests psychodynamic cause (i.e. that the conditions for sexual desire are present, but the person is, for some reason, inhibiting their own sexual interest.) The term "hypoactive sexual desire" is more awkward, but more neutral with respect to the cause. The DSM-III-R estimated that about 20% of the population had HSDD. In the DSM-IV (1994), the criterion that the diagnosis requires "marked distress or interpersonal difficulty" was added.
The DSM-5, published in 2013, split HSDD into male hypoactive sexual desire disorder and female sexual interest/arousal disorder. The distinction was made because men report more intense and frequent sexual desire than women. According to Lori Brotto, this classification is desirable compared to the DSM-IV classification system because: (1) it reflects the finding that desire and arousal tend to overlap (2) it differentiates between women who lack desire before the onset of activity, but who are receptive to initiation and or initiate sexual activity for reasons other than desire, and women who never experience sexual arousal (3) it takes the variability in sexual desire into account. Furthermore, the criterion of 6 symptoms be present for a diagnosis helps safeguard against pathologizing adaptive decreases in desire.
HSDD, as currently defined by the DSM has come under criticism of the social function of the diagnosis.
- HSDD could be seen as part of a history of the medicalization of sexuality by the medical profession to define normal sexuality. It has also been examined within a "broader frame of historical interest in the problematization of sexual appetite".
- HSDD has been criticized over pathologizing normal variations in sexuality because the parameters of normality are unclear. This lack of clarity is partly due to the fact that the terms "persistent" and "recurrent" do not have clear operational definitions.
- HSDD may function to pathologize asexuals, though their lack of sexual desire may not be maladaptive. Because of this, some members of the asexual community lobbied the mental health community working on the DSM-5 to regard asexuality as a legitimate sexual orientation rather than a mental disorder.
Other criticisms focus more on scientific and clinical issues.
- HSDD is such a diverse group of conditions with many causes that it functions as little more than a starting place for clinicians to assess people.
- The requirement that low sexual desire causes distress or interpersonal difficulty has been criticized. It has been claimed that it is not clinically useful because if it is not causing any problems, the person will not seek out a clinician. One could claim that this criterion (for all of the sexual dysfunctions, including HSDD) decreases the scientific validity of the diagnoses or is a cover-up for a lack of data on what constitutes normal sexual function.
- The distress requirement is also criticized because the term "distress" lacks a clear definition.
Prior to the publication of the DSM-5, the DSM-IV criteria were criticized on several grounds. It was suggested that a duration criterion should be added because lack of interest in sex over the past month is significantly more common than lack of interest lasting six months. Similarly, a frequency criterion (i.e., the symptoms of low desire be present in 75% or more of sexual encounters) has been suggested.
The current framework for HSDD is based on a linear model of human sexual response, developed by Masters and Johnson and modified by Kaplan consisting of desire, arousal, orgasm. The sexual dysfunctions in the DSM are based around problems at any one or more of these stages. Many of the criticisms of the DSM-IV framework for sexual dysfunction in general, and HSDD in particular, claimed that this model ignored the differences between male and female sexuality. Several criticisms were based on inadequacy of the DSM-IV framework for dealing with female's sexual problems.
- Increasingly, evidence shows that there are significant differences between male and female sexuality. Level of desire is highly variable from female to female and there are some females who are considered sexually functional who have no active desire for sex, but they can erotically respond well in contexts they find acceptable. This has been termed "responsive desire" as opposed to spontaneous desire.
- The focus on merely the physiological ignores the social, economic and political factors including sexual violence and lack of access to sexual medicine or education throughout the world affecting females and their sexual health.
- The focus on the physiological ignores the relationship context of sexuality despite the fact that these are often the cause of sexual problems.
- The focus on discrepancy in desire between two partners may result in the partner with the lower level of desire being labeled as "dysfunctional," but the problem really sits with difference between the two partners. However, within couples the assessment of desire tends to be relative. That is, individuals make judgments by comparing their levels of desire to that of their partner.
- The sexual problems that females complain of often do not fit well into the DSM-IV framework for sexual dysfunctions.
- The DSM-IV system of sub-typing may be more applicable to one sex than the other.
- Research indicates a high degree of comorbidity between HSDD and female sexual arousal disorder. Therefore, a diagnosis combining the two (as the DSM-5 eventually did) might be more appropriate.
- University of Maryland, Medical Centre: Inhibited sexual desire
- Frellick, Marcia. "FDA Approves New Libido-Boosting Drug for Premenopausal Women". Medscape. WebMD LLC. Retrieved 22 June 2019.
- Alison Ritter: Appropriate services for gay, lesbian, bisexual and transgender people: More than just gender sensitive? page 5
- American Psychiatric Association, ed. (2013). "Male Hypoactive Sexual Desire Disorder, 302.71 (F52.0)". Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. American Psychiatric Publishing. pp. 440–443.
- American Psychiatric Association, ed. (2013). "Female Sexual Interest/Arousal Disorder, 302.72 (F52.22)". Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. American Psychiatric Publishing. pp. 433–437.
- Diagnostic and Statistical Manual of Mental Disorders (3rd ed.). Washington DC: American Psychiatric Association. 1980.
- Munjack, Dennis, and Pamela Kanno. "An overview of outcome on frigidity: treatment effects and effectiveness." Comprehensive Psychiatry 17.3 (1976): 401-413.
- Janssen, E., Bancroft J. (2006). "The dual control model: The role of sexual inhibition & excitation in sexual arousal and behavior". In Janssen, E. (ed.). The Psychophysiology of Sex. Bloomington IN: Indiana University Press.CS1 maint: multiple names: authors list (link)
- Clayton AH (July 2010). "The pathophysiology of hypoactive sexual desire disorder in women". Int J Gynaecol Obstet. 110 (1): 7–11. doi:10.1016/j.ijgo.2010.02.014. PMID 20434725.
- Maurice, William (2007). "Sexual Desire Disorders in Men". In Leiblum, Sandra (ed.). Principles and Practice of Sex Therapy (4th ed.). New York: The Guilford Press.
- Balon, Richard (2007). "Toward an Improved Nosology of Sexual Dysfunction in DSM-V". Psychiatric Times. 24 (9).
- Brauer M, van leeuwen M, Janssen E, Newhouse SK, Heiman JR, Laan E (September 2011). "Attentional and Affective Processing of Sexual Stimuli in Women with Hypoactive Sexual Desire Disorder". Archives of Sexual Behavior. 41 (4): 891–905. doi:10.1007/s10508-011-9820-7. PMID 21892693.
- Rosen RC, Shifren JL, Monz BU, Odom DM, Russo PA, Johannes CB (June 2009). "Correlates of sexually-related personal distress in women with low sexual desire". Journal of Sexual Medicine. 6 (6): 1549–1560. doi:10.1111/j.1743-6109.2009.01252.x. PMID 19473457.
- Basson, Rosemary (2007). "Sexual Desire/Arousal Disorders in Women". In Leiblum, Sandra (ed.). Principles and Practice of Sex Therapy (4th ed.). New York: The Guilford Press.
- Jaspers, L; Feys, F; Bramer, WM; Franco, OH; Leusink, P; Laan, ET (1 April 2016). "Efficacy and Safety of Flibanserin for the Treatment of Hypoactive Sexual Desire Disorder in Women: A Systematic Review and Meta-analysis". JAMA Internal Medicine. 176 (4): 453–62. doi:10.1001/jamainternmed.2015.8565. PMID 26927498.
- Foley KF, DeSanty KP, Kast RE (September 2006). "Bupropion: pharmacology and therapeutic applications". Expert Rev Neurother. 6 (9): 1249–65. doi:10.1586/1473718.104.22.1689. PMID 17009913.
- Howland RH (2015). "Buspirone: Back to the Future". J Psychosoc Nurs Ment Health Serv. 53 (11): 21–4. doi:10.3928/02793695-20151022-01. PMID 26535760.
- Wierman, ME; Arlt, W; Basson, R; Davis, SR; Miller, KK; Murad, MH; Rosner, W; Santoro, N (Oct 2014). "Androgen therapy in women: a reappraisal: an endocrine society clinical practice guideline". The Journal of Clinical Endocrinology and Metabolism. 99 (10): 3489–510. doi:10.1210/jc.2014-2260. PMID 25279570.
- Peter Cryle and Alison Moore, Frigidity: An Intellectual History. Basingstoke: Palgrave Macmillan, 2011. ISBN 978-0-230-30345-4.
- Peter Cyle and Alison Moore, Frigidity at the Fin-de-Siècle, a Slippery and Capacious Concept, Journal of the History of Sexuality 19 (2) May 2010, 243-261.
- Relocating Marie Bonaparte’s Clitoris. Australian Feminist Studies 24 (60), April 2009, 149-165.
- Masters, William; Johnson, Virginia (1970). Human Sexual Inadequacy. Boston: Little Brown.
- Koedt, A. (1970). "The myth of the vaginal orgasm". In Escoffier, J. (ed.). Sexual revolution. New York: Thunder's Mouth Press. pp. 100–9. ISBN 978-1-56025-525-3.
- Irvine, Janice (2005). Disorders of Desire. Philadelphia: Temple University Press. p. 265.
- Kaplan, Helen Singer (1995). The Sexual Desire Disorders. New York: Taylor & Francis Group. pp. 1–2, 7.
- Kaplan 1995, pp. 7–8
- Brotto LA, Chik HM, Ryder AG, Gorzalka BB, Seal B (December 2005). "Acculturation and sexual function in Asian women". Archives of Sexual Behavior. 34 (6): 613–626. doi:10.1007/s10508-005-7909-6. PMID 16362246.
- Leiblum, Sandra; Rosen, Raymond (1988). Sexual Desire Disorders. The Guilford Press. p. 1.
- Irvine 2005, p. 172
- Apfelbaum, Bernard (1988). "An Ego Analytic Perspective on Desire Disorders". In Lieblum, Sandra; Rosen, Raymond (eds.). Sexual Desire Disorders. The Guilford Press.
- American Psychological Association (1987)
- Brotto LA (2010). "The DSM Diagnostic Criteria for Hypoactive Sexual Desire Disorder in Women". Archives of Sexual Behavior. 39 (2): 221–239. doi:10.1007/s10508-009-9543-1. PMID 19777334.
- Brotto LA (June 2010). "The DSM Diagnostic Criteria for Hypoactive Sexual Desire Disorder in Men". Archives of Sexual Behavior. 7 (6): 2015–2030. doi:10.1111/j.1743-6109.2010.01860.x. PMID 20929517.
- Irvine 2005, pp. 175–6
- Flore, Jacinthe (2016). "The problem of sexual imbalance and techniques of the self in the Diagnostic and Statistical Manual of Mental Disorders". History of Psychiatry. 27 (3): 320–335. doi:10.1177/0957154X16644391. PMID 27118809.
- Flore, Jacinthe (2013). "HSDD and asexuality: a question of instruments". Psychology & Sexuality. 4 (2): 152–166. doi:10.1080/19419899.2013.774163.
- Prause N, Graham CA (June 2007). "Asexuality: classification and characterization" (PDF). Arch Sex Behav. 36 (3): 341–56. doi:10.1007/s10508-006-9142-3. PMID 17345167. Archived from the original (PDF) on 2008-10-02.
- Asexuals Push for Greater Recognition. http://abcnews.go.com/Health/MindMoodNews/story?id=6656358&page=1
- Bancroft J, Graham CA, McCord C (2001). "Conceptualizing women's sexual problems". J Sex Marital Ther. 27 (2): 95–103. doi:10.1080/00926230152051716. PMID 11247236.
- Althof SE (2001). "My personal distress over the inclusion of personal distress". J Sex Marital Ther. 27 (2): 123–5. doi:10.1080/00926230152051761. PMID 11247205.
- Bancroft J, Graham CA, McCord C (2001). "Conceptualizing Women's Sexual Problems". Journal of Sex & Marital Therapy. 27 (2): 95–103. doi:10.1080/00926230152051716. PMID 11247236.
- Mitchell KR, Mercer CH (September 2009). "Prevalence of Low Sexual Desire among Women in Britain: Associated Factors". The Journal of Sexual Medicine. 6 (9): 2434–2444. doi:10.1111/j.1743-6109.2009.01368.x. PMID 19549088.
- Balon R (2008). "The DSM Criteria of Sexual Dysfunction: Need for a Change". Journal of Sex and Marital Therapy. 34 (3): 186–97. doi:10.1080/00926230701866067. PMID 18398759.
- Segraves R, Balon R, Clayton A (2007). "Proposal for Changes in Diagnostic Criteria for Sexual Dysfunctions". Journal of Sexual Medicine. 4 (3): 567–580. doi:10.1111/j.1743-6109.2007.00455.x. PMID 17433086.
- Tiefer L, Hall M, Tavris C (2002). "Beyond dysfunction: a new view of women's sexual problems". J Sex Marital Ther. 28 (Suppl 1): 225–32. doi:10.1080/00926230252851357. PMID 11898706.
- Graham, CA (September 2010). "The DSM Diagnostic Criteria for Female Sexual Arousal Disorder". Archives of Sexual Behavior. 39 (2): 240–255. doi:10.1007/s10508-009-9535-1. PMID 19777335.
- Peter Cryle and Alison Moore, Frigidity: An Intellectual History. Basingstoke: Palgrave Macmillan, 2011. ISBN 978-0-230-30345-4.
- Peter Cryle and Alison Moore, Frigidity at the Fin-de-Siècle, a Slippery and Capacious Concept, Journal of the History of Sexuality 19 (2) May 2010, 243-261.
- Alison Moore, Frigidity, Gender and Power in French Cultural History – From Jean Fauconney to Marie Bonaparte. French Cultural Studies20 (4), November 2009, 331-349.
- Alison Moore, The Invention of the Unsexual: Situating Frigidity in the History of Sexuality and in Feminist Thought. French History and Civilization 2 (2009), 181-192.
- Montgomery, KA (Jun 2008). "Sexual Desire Disorders". Psychiatry (Edgmont). 5 (6): 50–55. PMC 2695750. PMID 19727285.
- Basson, R; Leiblum, S; Brotto, L; Derogatis, L; Fourcroy, J; Fugl-Meyer, K; Graziottin, A; Heiman, JR; Laan, E; Meston, C; Schover, L; van Lankveld, J; Schultz, WW (Dec 2003). "Definitions of women's sexual dysfunction reconsidered: advocating expansion and revision". Journal of Psychosomatic Obstetrics and Gynaecology. 24 (4): 221–9. doi:10.3109/01674820309074686. PMID 14702882.
- Warnock, JJ (2002). "Female hypoactive sexual desire disorder: epidemiology, diagnosis and treatment". CNS Drugs. 16 (11): 745–53. doi:10.2165/00023210-200216110-00003. PMID 12383030.
- Basson, R (10 May 2005). "Women's sexual dysfunction: revised and expanded definitions". Canadian Medical Association Journal. 172 (10): 1327–1333. doi:10.1503/cmaj.1020174. PMC 557105. PMID 15883409.
- Nappi, RE; Wawra, K; Schmitt, S (Jun 2006). "Hypoactive sexual desire disorder in postmenopausal women". Gynecological Endocrinology. 22 (6): 318–23. doi:10.1080/09513590600762265. PMID 16785156.