Migration or Ethnic Minority Status and Risk of Autism Spectrum Disorders and Intellectual Disability: Systematic and Scoping Reviews
Objectives: To investigate whether any such association is specific to ASD or ID and whether the severity of ASD or ID plays a role; to examine whether any increased risks of being diagnosed with ASD and ID results from migration-related factors or ethnically determined factors; and to explore potential underlying mechanisms for any association.
Methods: In the systematic review, a systematic literature search was conducted for observational studies that reported on proportion, prevalence, odds ratio or relative risks of ASD and/or ID among immigrants and/or ethnic minorities. Risks of any ASD, ASD+ID, ASD–ID, and any ID were reviewed regarding different migration and ethnic minority status, with consideration of study quality. In the scoping review, possible underlying mechanisms suggested in the included studies were summarized.
Results: 35 unique studies were included in the review. The results indicated an increased risk of ASD+ID and severe ID and a decreased risk of ASD–ID and mild ID in children of immigrant parents and those with ethnic minority status. The association appeared more pronounced with maternal immigrant status, with parental origin in low-income countries, and among second generation migrants. The suggested potential underlying mechanisms were environmental factors in pregnancy and genetic factors for ASD+ID and severe ID and ascertainment bias for ASD–ID and mild ID.
Conclusions: Migration-related factors may be more important drivers of ASD risk in immigrants than ethnically determined factors. The increased risk of severe types of ASD and ID may depend on such migration-related factors, and the decreased risk of milder types may depend on underdiagnosis.