The Disappearing Seasonality Of Autism Conceptions in California
Autism rates have increased dramatically in the last two decades. The autism caseload in California increased 600% between 1992 and 2006, yet there is little consensus as to cause. Studying the seasonality of conceptions of children later diagnosed with autism may yield clues to potential etiological drivers. We search for excess risk of conceptions of children later diagnosed with autism from 1992 to 2000 using case and control data from California, adaptive temporal windows and a one-dimensional scan statistic. We test for confounding by known risk factors in the cluster period using logistic regressions. There is a consistent but decreasing seasonal pattern in the risk of conceiving a child later diagnosed with autism in November for the first half of the study period. Temporal clustering of autism conceptions is not an artifact of composition with respect to known risk factors for autism, such as socio-economic status. Therefore, search for environmental factors related to autism should allow for the possibility of risk factors or etiological drivers that are seasonally patterned and that appear to remain salient for a discrete number of years.
Read our paper: Mazumdar, S., Liu, K., Susser, E., & Bearman, P.S. (2012) The Disappearing Seasonality of Autism Conceptions in California. PLoS One, Volume 7, Issue 7:e41265.