title: Autism prevalence and precipitation rates in California, Oregon, and Washington counties.
abstract: OBJECTIVE
  To investigate empirically the possibility of an environmental trigger for autism among genetically vulnerable children that is positively associated with precipitation.
  
  
  METHODS
  We used regression analysis to investigate autism prevalence rates and counts first in relation to mean annual county-level precipitation and then to the amount of precipitation a birth cohort was exposed to when younger than 3 years, controlling for time trend, population size, per capita income, and demographic characteristics. In some models, we included county fixed-effects rather than a full set of covariates.
  
  
  METHODS
  Counties in California, Oregon, and Washington.
  
  
  METHODS
  Children born in California, Oregon, and Washington between 1987 and 1999. Main Exposure County-level precipitation.
  
  
  METHODS
  County-level autism prevalence rates and counts.
  
  
  RESULTS
  County-level autism prevalence rates and counts among school-aged children were positively associated with a county's mean annual precipitation. Also, the amount of precipitation a birth cohort was exposed to when younger than 3 years was positively associated with subsequent autism prevalence rates and counts in Oregon counties and California counties with a regional developmental services center.
  
  
  CONCLUSIONS
  These results are consistent with the existence of an environmental trigger for autism among genetically vulnerable children that is positively associated with precipitation. Further studies focused on establishing whether such a trigger exists and identifying the specific trigger are warranted.
authors.affiliation: Johnson Graduate School of Management, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Waldman
authors.forename: Sean
authors.initials: S
authors.lastname: Nicholson
authors.forename: Nodir
authors.initials: N
authors.lastname: Adilov
authors.forename: John
authors.initials: J
authors.lastname: Williams
mesh_terms: D000293:Adolescent; D001321:Autistic Disorder / Q000453:epidemiology* / Q000209:etiology* / Q000235:genetics; D002140:California / Q000453:epidemiology; D002391:Catchment Area, Health; D002648:Child; D002980:Climate; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D009922:Oregon / Q000453:epidemiology; D015995:Prevalence; D014861:Washington / Q000453:epidemiology