RE: A further plea for adherence to the principles underlying science in general and the epidemiologic enterprise in particular.

or possible causal mechanisms that could lead to changes in incidence. Here I try to meet this latter need. I have adduced very substantial quantities of data to support the hypothesis that mammalian (including human) sex ratios (proportions male) at birth are partially controlled by the hormone levels of both parents around the time of conception. 2–5 Baron-Cohen 6 hypothesized that one cause of autism is high maternal intrauterine concentrations of testos-terone. If both hypotheses were correct, then sibs of autistic probands should contain an excess of brothers. I reported evidence for such an inference at a statistically significant level, 7 and this finding has itself been confirmed. 8 So there is good evidence for Baron-Cohen's hypothesis that one cause of autism is high maternal intrauterine testosterone concentration. There is good reason to suppose that over the past few decades, there has been an increase in women's testosterone levels. Such an increase would be expected to have been associated with the rise in rates of diabetes , 9,10 and of obesity 11 in women. Thus, it seems reasonable to propose that the reported increase in rates of autism is at least partially real and due to increasing maternal intrauterine testosterone levels. 2 James WH. Evidence that mammalian sex ratios at birth are partially controlled by parental hormone levels at the time of conception. 3 James WH. Further evidence that mammalian sex ratios at birth are partially controlled by parental hormone levels around the time of conception. 4 James WH. Evidence that mammalian sex ratios at birth are partially controlled by parental hormone levels around the time of conception. 5 James WH. Further evidence for the hypothesis that parental hormone levels around the time of conception are associated with human sex ratios at birth. 7 James WH. Further evidence that some male-based neurodevelopmental disorders are associated with high intrauterine testosterone concentrations. Sibling sex ratio of individuals diagnosed with autism spectrum disorder as children. profile of women with non-insulin-dependent diabetes mellitus. Free testoster-one levels during the menstrual cycle in obese versus normal women. Boffetta et al. 1 suggest that the participation of one of us (M.H.) in an International Agency for Research on Cancer (IARC) Working Group as an author of a paper about a large cohort study on occupational formaldehyde exposure 2 may have given that study an 'overly important role' when the IARC decided to upgrade formaldehyde from probably carcinogenic …