There are several known epidemiological differences between the genders in psychiatric disorders. Does this also extend to differences in responses to treatment?
Depression and its treatment
No good evidence for different therapeutic effects on women and men with MDD
The heritability of major depressive disorder (MDD) is greater for women than men.1 Likewise, its lifetime prevalence is higher for women.2 Although the difference in incidence between the genders diminishes in post-menopausal women, the severity, disease duration and rates of recurrence are generally higher for women, so their disease course is often a more severe one. The effectiveness of antidepressants in treating MDD of at least moderate severity is well established.3 Several systematic reviews and meta-analyses have also investigated whether there are differences in the efficacy of antidepressant therapies in women and men. These demonstrate no good evidence for different therapeutic effects in women and men, or for a change in efficacy related to menopausal status in women.
Bipolar I disorder and its treatment
Women with bipolar I disorder often have a more severe disease course than men
The lifetime prevalence of bipolar I disorder is around 0.6%, a prevalence about the same in women and men. Despite this equal prevalence, however, bipolar I is a diverse disorder, with a great deal of inter-individual disease variation, and women tend to demonstrate a more severe disease course than men.5 Thus, women with bipolar I are more likely to attempt suicide,6 have greater rates of in-patient admissions,7 and are more likely to experience rapid cycling and mixed episodes,8 both of which are indicative of a more severe disease course. Women with bipolar I disorder therefore often show a worse prognosis of their disorder than do men. This difference between the genders cannot, however, be explained by any difference in their response to pharmacotherapy for manic episodes. An individual patient meta-analysis in mania showed slightly better treatment efficacy in men than women, but these differences did not reach statistical significance. This effect was also independent of patient age greater or less than 47 years (a proxy for menopausal status).
Schizophrenia and treatment with antipsychotics
Men showed a larger placebo response than women in trials of antipsychotics
Potential difference in the effects of antipsychotics on women and men with schizophrenia were investigated using data from the NewMeds database.9,10 These data from 64 studies, involving 25,900 patients, did show a better treatment response (comparing active treatment with placebo) in women than in men. However, this difference was attributable to a larger placebo response in men, which reduced the apparent treatment effect when compared with women, who showed a smaller placebo response. The reason for this difference between the genders is unknown; but was robust across different studies. One possible explanation is a greater response of male patients to the social and environmental changes (and comforts) produced by being included in a trial cohort (leading to an enhanced placebo response). All of these results merit further investigation, so that treatments can increasingly be tailored to individual patients.
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