Individual behaviors were modeled as indicators of an Externalizing factor at each individual wave; these wave-specific factors, in turn, loaded on a higher-order Persistent Externalizing factor (Figure 1). Loadings for individual behaviors (e.g., hazardous alcohol use) on the wave-specific Externalizing factors were constrained to be equal a priori across all waves.1 Residual covariances among measures of the same behavior at different waves were modeled with a series of domain-specific factors (Alcohol Use, Cannabis Use, Property Crime, Tobacco Use, Risky Sex, and Sensation Seeking/ZK Impulsivity). Factor models were estimated using Mplus version 7.31 (Muthén & Muthén, Los Angeles, CA), and model fit was evaluated using root mean square error of approximation (RMSEA), with values less than 0.05 indicating good fit (Steiger, 1990). We also used the Bentler Comparative Fit Index (CFI) and Tucker-Lewis Index (TLI) indices, which are sensitive to model fit as well as parsimony. Values of CFI and TLI vary between 0 and 1 with excellent values being greater than 0.95 (Hu & Bentler, 1999). Factor scores for the Persistent Externalizing factor and the six domain-specific factors were then estimated using Mplus, and these factor score estimates were used as the phenotypes in all subsequent analyses.
