Standardized estimates (variance component divided by total variance) of additive genetic, common environmental, and unique environmental influences on age 14 alcohol use frequency and age 12 behavior problems are presented in Table 1. Constraining the variance components equal between males and females caused a significant decrease in fit for both alcohol use frequency (χ2Δ = 19.18, 3 df, p < 0.01) and behavior problems (χ2Δ = 8.47, 3 df, p = 0.04). For alcohol use frequency, the A and C parameters could be constrained equal (for A: χ2Δ <0.01, 1 df, p = 0.98; for C: χ2Δ = 1.36, 1 df, p = 0.24); however, constraining the E parameter caused a significant decrease in fit (χ2Δ = 15.38, 1 df, p < 0.01). For behavior problems, constraining both the A and C pathways equal caused a significant decrease in fit (χ2Δ = 8.47, 2 df, p = 0.01). Dropping the paths separately suggested that the significance was more strongly related to constraining the A pathway (dropping A: χ2Δ = 3.13, 1 df, p = 0.08; dropping C: χ2Δ = 1.76,
