The Autism Birth Cohort: a paradigm for gene–environment–timing research

The reported prevalence of autism spectrum disorders (ASD) has increased 5–10× over the past 20 years. Whether ASD are truly more frequent is controversial; nonetheless, the burden is profound in human and economic terms. Although autism is among the most heritable of mental disorders, its pathogenesis remains obscure. Environmental factors are proposed; however, none is implicated. Furthermore, there are no biomarkers to screen for ASD or risk of ASD. The Autism Birth Cohort (ABC) was initiated to investigate gene × environment × timing interactions and enable early diagnosis. It employs a large, unselected birth cohort wherein cases are prospectively ascertained through population screening. Samples collected serially through pregnancy and childhood include parental blood, maternal urine, cord blood, milk teeth and rectal swabs. More than 107 000 children are continuously screened via questionnaires, referral and a national registry. Cases are compared with a control group from the same cohort in a “nested case-control” design. Early screening, diagnostic assessments and re-assessments are designed to provide a rich view of longitudinal trajectory. Genetic, proteomic, immunologic, metagenomic and microbiological tools will be used to exploit unique biological samples. The ABC is a paradigm for investigating the role of genetic and environmental factors in complex disorders.