Figure 2.
Multivariate causal model of initiation and progression of smoking and initiation and progression of cannabis and other illicit drug use. IS = initiation of smoking, PS = progression of smoking; IC = initiation of cannabis use; PC = progression of cannabis use; AIS = additive genetic influences on initiation of smoking; CIS = common/shared environmental influences on initiation of smoking; EIS = unique/unshared environmental influences on initiation of smoking; APS = additive genetic influences on progression of smoking; EPS = unique environmental influences on progression of smoking; AIC = additive genetic influences on initiation of cannabis use; CIC = common environmental influences on initiation of cannabis use; EIC = unique environmental influences on initiation of cannabis use; EPC = unique environmental influences on progression of cannabis use. Numbers reflect the respective path coefficients.