title: The disappearing seasonality of autism conceptions in California.
abstract: BACKGROUND
  Autism incidence and prevalence 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 the cause. Studying the seasonality of conceptions of children later diagnosed with autism may yield clues to potential etiological drivers.
  
  
  OBJECTIVE
  To assess if the conceptions of children later diagnosed with autism cluster temporally in a systematic manner and whether any pattern of temporal clustering persists over time.
  
  
  METHODS
  We searched for seasonality in conceptions of children later diagnosed with autism by applying a one-dimensional scan statistic with adaptive temporal windows on case and control population data from California for 1992 through 2000. We tested for potential confounding effects from known risk factors using logistic regression models.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  There is some evidence of seasonality in the risk of conceiving a child later diagnosed with autism. Searches for environmental factors related to autism should allow for the possibility of risk factors or etiological drivers that are seasonally patterned and that appear and remain salient for a discrete number of years.
authors.affiliation: Paul F Lazarsfeld Center for the Social Sciences, Columbia University, New York, New York, United States of America. soumyamazumdar@yahoo.com
authors.forename: Soumya
authors.initials: S
authors.lastname: Mazumdar
authors.forename: Ka-Yuet
authors.initials: KY
authors.lastname: Liu
authors.forename: Ezra
authors.initials: E
authors.lastname: Susser
authors.forename: Peter
authors.initials: P
authors.lastname: Bearman
mesh_terms: D001321:Autistic Disorder / Q000453:epidemiology* / Q000209:etiology; D002140:California / Q000453:epidemiology; D016000:Cluster Analysis; D005260:Female; D006801:Humans; D016013:Likelihood Functions; D016015:Logistic Models; D008297:Male; D008954:Models, Biological; D009010:Monte Carlo Method; D016017:Odds Ratio; D012306:Risk; D012621:Seasons