title: Letter: Emigration and mental subnormality in Northern Ireland.
mesh_terms: D000293:Adolescent; D000328:Adult; D004314:Down Syndrome / Q000453:epidemiology*; D004641:Emigration and Immigration; D006306:Health Surveys; D006801:Humans; D008607:Intellectual Disability / Q000453:epidemiology*; D009660:Northern Ireland