Multivariate analysis of familial and non-familial influences for commonality in drug use

A multivariate behavioral genetic analysis of common legal drug usage was performed on data from 238 Swedish families. By calculating cross-covariances between parents and offspring for pairs of traits, familial and non-familial correlations were computed to determine the extent to which pairs of measures share the same familial and non-familial influences. Factor analyses resulted in a 3- and a 2-factor solution for the familial and non-familial correlations, respectively. This suggests that familial and non-familial influences for drug usage are structured differently. If replicable, these results also suggest that the phenotypic structure reflects familial factors more than non-familial influences.