Fig. 1.

Parameter estimates from the best-fitting common pathway model for cannabis, stimulant and sedative abuse in Swedish male–male twin and near-aged sibling pairs. (A, C and E) refer, respectively, to additive genetic, shared environmental, and unique environmental risk factors. The subscript “c” refers to risk factors on the common latent factor, here labeled “vulnerability to drug abuse.” The subscript “s” refers to risk factors specific to the abuse of individual substance classes. The paths from the common latent factor to the individual forms of drug abuse reflect the degree to which those forms of drug abuse index the liability to the latent factor.