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→Mental disorders significantly reduce male fertility, substantially more than they do for women
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===<span style="font-family:'Linux Libertine, Georgia, Times, serif'; font-size:24px; font-weight: normal;">Mental disorders significantly reduce male fertility, substantially more than they do for women</span>=== | ===<span style="font-family:'Linux Libertine, Georgia, Times, serif'; font-size:24px; font-weight: normal;">Mental disorders significantly reduce male fertility, substantially more than they do for women</span>=== | ||
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https://jamanetwork.com/journals/jamapsychiatry/article-abstract/1390257 | A study in 2013 examining a total of 2.3 million individuals born in Sweden in 1950-1970, using government health care records, found evidence for substantially lower fertility among sufferers of various mental illnesses. The fertility of the mentally ill was computed by measuring the fertility ratio (e.g. a FR of 0.5 would mean that the diseased group had on average half of the children of the general non-affected population, a FR of 2 would mean double the offspring on average) which reflected the mean number of children that individuals with various mental disorders had, as compared to control individuals of the same age and sex, also accounting for variables family size, affected status and parental status. The youngest individuals involved, at the time their data was recorded, were 40 years old, and had thus likely largely completed their reproductive careers. | ||
The researchers found evidence of substantially strong selection pressure against schizophrenia (male FR .23 vs female FR .47) , autism (male FR .25 vs female FR .48), and anorexia nervosa (male FR 0.54 vs female FR .81), but not bi-polar disorder. Depression (weakly for men (FR .93), not at all for women) and substance abuse disorders (male FR .78 vs female FR .92) were also being selected against, but to a lesser degree than the previously mentioned conditions. It was also found that the selection pressure against these disorders was found to be consistently higher much among men who suffered from them, as compared to the women who suffered from these conditions. This is in accordance with [[Bateman's principle]], which suggests that males of most species have greater reproductive variance than females. | |||
The researchers also found evidence that the fertility siblings of those with mental disorders was generally lower also, with it also being discovered that the fertility of the male siblings of those with certain mental disorders was generally lower than their female siblings, similar to the relationship that was discovered regarding the differential effects of mental illness on fertility being moderated by sex. | |||
However there was also evidence that siblings of those that suffered from depression had a larger number of children on average, indicating that balancing selection was operating on genes associated with propensity to depression, i.e. the fertility cost to the sufferers of the condition is potentially balanced by the increased fecundity of their siblings. The researchers also discovered a similar relationship regarding substance abuse being associated with balancing selection, likely due to the association of this condition with genes involved in greater risk tasking propensity, which has been shown to be related to greater sexual success. | |||
The researchers concluded that schizophrenia and autism were under purifying selection in modern Western societies, with the high continuing prevalence of these conditions possibly being maintained through new mutations (possibly due to increased paternal age), and that it has been also been supported by prior research (MacCabe et al., 2009) that the sufferers of these conditions lower fertility is likely largely due to the sufferers of these conditions being less able to find a partner to marry/have children with, with this being stronger among males who suffer from mental illness. | |||
<span style="font-size:125%">'''Quotes:'''</span> | |||
* ''Except for women with depression, affected patients had significantly fewer children (FR range for those with psychiatric disorder, 0.23-0.93; P < 10−10). This reduction was consistently greater among men than women, suggesting that male fitness was particularly sensitive.'' | |||
* ''Individuals with autism showed the greatest reduction in fecundity among all examined disorders. This was not unexpected because previous investigations have shown that few individuals with autism ever married or had children [...]'' | |||
* ''Our results suggest that strong selection exists against schizophrenia, autism, and anorexia nervosa and that these variants may be maintained by new mutations or an as-yet unknown mechanism.'' | |||
* ''Depression and, to a lesser extent, substance abuse, seems to be maintained by genes that are beneficial under some circumstances (ie, in siblings) but detrimental in others (i.e, affected individuals).'' | |||
<span style="font-size:125%">'''References:'''</span> | |||
*Power RA, Kyaga S, Uher R. et al. 2013. ''Fecundity of Patients With Schizophrenia, Autism, Bipolar Disorder, Depression, Anorexia Nervosa, or Substance Abuse vs Their Unaffected Siblings.'' Jama Psychiatry, 70(1):22-30. [[https://jamanetwork.com/journals/jamapsychiatry/article-abstract/1390257 FullText]] | |||
==''Race''== | ==''Race''== | ||