Parental Socioeconomic Status and Risk of Offspring Autism Spectrum Disorders

Background: The over-representation of autism spectrum disorders (ASD) in children of high socioeconomic status (SES) families is one of the oldest controversies in autism literature, but consistently reported in the USA. These findings starkly contrast with SES gradients of many health conditions, and may result from SES inequalities in access to services.

Objectives: To test the hypothesis that children from lower SES families would be at greater risk of ASD, once case-ascertainment biases are minimized.

Methods: We tested this hypothesis in a population-based study in Sweden, which has universal healthcare, free routine screening for developmental problems for all children, and thorough protocols for multidisciplinary diagnoses of ASD. In a case-control study nested in a total-population cohort of children aged 0-17 years, living in Stockholm County between 2001-2007 (n=589,114), we matched ASD cases (n=4709) by age and sex to ten randomly selected controls by age and sex. 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 relationship with parental education was observed. These associations were present after accounting for parental ages, migration status, parity, and psychiatric service use, maternal smoking during pregnancy and birth characteristics; and were present 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. Social stressors need to be considered in the etiology of ASD.