Circannual pattern of autistic births: reanalysis in three ethnic groups.

Seasonal variations in births of autistic subjects have been reported for the United States, Canada, Sweden, Japan, and Israel. Here, data from England, Japan, and Israel are reanalyzed using spectral analysis for the cosine function. A sample of 583 autistic births occurring over 40 years (1947-1989) is meta-analyzed, focusing on rhythmicity. Major periodicities of 17.6, 18.6, and 21.8 years, on which minor periodicities ranging from 2.2 to 4.1 years were superimposed, yielded the best-fitting cosine function to significantly explain variance of autistic birth patterns. It is interesting that the function composed of a major period with several minor periods is remarkably similar in each of the three ethnic groups. In all three countries the acrophases (calculated function) aggregate in the period 1963-1970. In light of this apparent universality of rhythms in autistic births across continents, we call for further investigations into the role of environmental factors, possibly viral pandemics, in the etiology of autism.