Lalit Srivastava raises a small, but important point about the patterning in the incidence of psychotic disorders between men and women. We suggested our data showed a "secondary peak" for women with schizophrenia after their mid-forties (Fig. S4). It is perhaps more accurate to say that this figure shows a decline in schizophrenia with advanced age for both men and women, but that this decline is sharper in men, such that the point estimates of pooled incidence of schizophrenia for women become non-significantly higher than for men after around age 45. This interaction was confirmed by fractional polynomial meta-regression in our analysis. We note that for the affective psychoses we did see a significant upward increase in the pooled incidence of disorder after age 45 years in women (see our paper). When taken together (i.e., looking at all clinically relevant psychoses), the available data in England were suggestive of this interaction between age and sex.
Due to space, we were not able to include every figure from every analysis in our PLoS ONE paper, but our full data (showing age by sex figures for each disorder considered) are available in our report to the Department of Health. Interested readers should visit this website.
We thank Lalit Srivastava for bringing this important point to bear; for some disorders, the typically assumed "secondary peak" may be a slower decline, rather than an upward trend. We suggest this possibility is considered in future, well-conducted individual incidence studies in other settings.
View all comments by James Kirkbride
I read with interest this thorough review and meta-analyses on the incidence of schizophrenia and other psychoses in England. The authors state that "a secondary peak in incidence for women, commencing in their mid- to late forties," was found, and cite Fig. S4 (page 7). I have difficulty seeing a second peak of incidence of schizophrenia in women in Fig. S4. Perhaps the authors or other epidemiologists can clarify this further. This is important, because most people in the field commonly believe that women have a second peak of onset of schizophrenia after their forties, related perhaps to a decline in estrogen levels.View all comments by Lalit Srivastava