H. Kunugi et al., SCHIZOPHRENIA FOLLOWING IN-UTERO EXPOSURE TO THE 1957 INFLUENZA EPIDEMICS IN JAPAN, The American journal of psychiatry, 152(3), 1995, pp. 450-452
Objective: Studies in Finland, England, and Denmark have reported that
individuals exposed to the 1957 A2 influenza pandemic during their se
cond trimester in utero are at greater risk for later schizophrenia. H
owever, other studies in England, the United States, and Holland repor
ted no such association. The authors' goal was to shed light on these
conflicts. Method: They compared the number of individuals who later d
eveloped schizophrenia who were born in the 5 months after the peak pr
evalence of three distinct 1957 influenza epidemics in Japan with the
mean number of individuals who later developed schizophrenia who were
born in the corresponding months of the 4 years surrounding the epidem
ics. Results: A significantly greater number of females but not males
who later developed schizophrenia were born during the risk exposure m
onths than In the non-risk-exposure months. Conclusions: These finding
s, although weak, lend support to the claim that in utero exposure to
influenza epidemics is a risk factor for adult schizophrenia.