title: Parental socioeconomic status and risk of offspring autism spectrum disorders in a Swedish population-based study.
abstract: OBJECTIVE
  Epidemiological studies in the United States consistently find autism spectrum disorders (ASD) to be overrepresented in high socioeconomic status (SES) families. These findings starkly contrast with SES gradients of many health conditions, and may result from SES inequalities in access to services. We hypothesized that prenatal measures of low, not high, parental SES would be associated with an increased risk of offspring ASD, once biases in case ascertainment are minimized.
  
  
  METHODS
  We tested this hypothesis in a population-based study in Sweden, a country that has free universal healthcare, routine screening for developmental problems, and thorough protocols for diagnoses of ASD. In a case-control study nested in a total population cohort of children aged 0 to 17 years living in Stockholm County between 2001 and 2007 (N = 589,114), we matched ASD cases (n = 4,709) by age and sex to 10 randomly selected controls. We retrieved parental SES measures collected at time of birth by record linkage.
  
  
  RESULTS
  Children of families with lower income, and of parents with manual occupations (OR = 1.4, 95% CI = 1.3-1.6) were at higher risk of ASD. No important relationships with parental education were observed. These associations were present after accounting for parental ages, migration status, parity, psychiatric service use, maternal smoking during pregnancy, and birth characteristics; and regardless of comorbid intellectual disability.
  
  
  CONCLUSIONS
  Lower, not higher, socioeconomic status was associated with an increased risk of ASD. Studies finding the opposite may be underestimating the burden of ASD in lower SES groups.
authors.affiliation: Academic Unit of Psychiatry, School of Social and Community Medicine, University of Bristol, Oakfield house, Oakfield Grove, Clifton, Bristol, BS8 2BN, UK. dheeraj.rai@bristol.ac.uk
authors.forename: Dheeraj
authors.initials: D
authors.lastname: Rai
authors.forename: Glyn
authors.initials: G
authors.lastname: Lewis
authors.forename: Michael
authors.initials: M
authors.lastname: Lundberg
authors.forename: Ricardo
authors.initials: R
authors.lastname: Araya
authors.forename: Anna
authors.initials: A
authors.lastname: Svensson
authors.forename: Christina
authors.initials: C
authors.lastname: Dalman
authors.forename: Peter
authors.initials: P
authors.lastname: Carpenter
authors.forename: Cecilia
authors.initials: C
authors.lastname: Magnusson
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D002659:Child Development Disorders, Pervasive / Q000453:epidemiology* / Q000209:etiology*; D002675:Child, Preschool; D015331:Cohort Studies; D015897:Comorbidity; D003430:Cross-Sectional Studies; D004522:Educational Status; D004651:Employment / Q000145:classification; D005260:Female; D006801:Humans; D007182:Income; D007223:Infant; D007231:Infant, Newborn; D008607:Intellectual Disability / Q000453:epidemiology / Q000209:etiology; D008297:Male; D010290:Parents; D011247:Pregnancy; D012307:Risk Factors; D012923:Social Class; D013548:Sweden