Season of birth and autistic disorder in Israel.

OBJECTIVE

Variations in month of birth were examined in patients with infantile autism to test the hypothesis that birth in a particular month may be a risk factor for this disorder.

METHOD

Data for autistic patients registered with the National League for Autism in Israel (N = 188) during the years 1964-1986 were compared with data on monthly distribution of live births in Israel for the corresponding period.

RESULTS

After risk ratio estimates were computed for children born with infantile autism for each month, a significant increase was observed for children born in March and August. This association was true for each year throughout the study. An additional finding was a significantly higher rate of birth of autistic children in the years 1970-1976.

CONCLUSIONS

This study, although made in a different climatic area than three earlier studies, further emphasizes the earlier findings that March and August births are a risk factor for development of autistic disorder.