Migration status and severity of autism spectrum disorder: A retrospective study at two specialist centers in Northern Italy.

Background and Aim: Migration has emerged as an environmental factor potentially contributing to the development of autism spectrum disorder (ASD). However, relatively little is known about the relationship between migration status and ASD severity. Materials and Methods: We retrospectively reviewed the geographical area of origin of 184 children with ASD (138 males, 75.0%) at two specialist centers in Northern Italy to assess possible correlations between migration status and ASD severity. Results: Based on migration status, 99 patients were classed as immigrant (74 males, 74.7%) and 85 as nonimmigrant (64 males, 75.3%). The severity of ASD was significantly higher in the immigrant group compared to the nonimmigrant group (2 = 16.32; P < 0.001). Specifically, ASD severity was significantly higher in patients migrating from Asia (2 = 10.85; P = 0.004) and Africa (2 = 6.26; P = 0.044), but not from South America (2 = 2.75; P = 0.253) or from Eastern Europe (2 = 2.76; P = 0.252). Conclusion: Immigrant patients have an increased risk of developing more severe ASD compared to nonimmigrants. Migration‑related maternal stress has been proposed as an environmental factor possibly contributing to the development of more severe ASD. Linguistic and/or sociocultural proximity have been hypothesized to account for the lower severity of ASD in Hispanic immigrants from South America and Eastern‑European White immigrants, compared to immigrants from Asia and Africa.