Environmental clustering of drug abuse in households and communities: multi-level modeling of a national Swedish sample
Both epidemiological and genetically informative studies indicate that shared environmental influences contribute to resemblance in siblings for drug abuse (DA). To what degree do these influences arise from living in the same household versus residing in the same community? We performed a cross-classified multi-level logistic regression on all individuals born in Sweden 1975-1990 (N = 1558,654).