Table 5 shows the results of models examining the significance of parameters in the Common Pathway Model. Parameter tests confirmed the presence of the latent trait in males and females, as well as similar magnitudes of effect across genders for (i) the factor structure of the latent trait (further referred to as Substance Dependence Vulnerability (SDV)), and (ii) the magnitude of genetic and environmental effects on SDV. Furthermore, the removal of shared environmental effects on SDV resulted in a more significant improvement in model fit, relative to the removal of additive genetic effect on SDV. It is also important to note that although we had limited power to distinguish between the A and C effects, there were significant familial effects on SDV in males and females. In regards to the substance-specific variance, the parameter tests confirmed the presence of significant familial effects on alcohol and tobacco in males and females, but limited familial effects on cannabis (more so in males (Δχ2 = 1.57, Δdf = 2, P = 0.45, ΔAIC = −2.43) than females (Δχ2 = 4.26, Δdf = 2,
