Investigating Trivariate Associations Between Risky Sexual Behavior, Internalizing Problems, and Externalizing Problems: A Twin Study.

Risky sexual behavior (RSB) has been linked to externalizing problems, substance use, and, in a recent study by our lab, internalizing problems. The current study builds upon previous work investigating the relationship between RSB and internalizing problems (INT) by controlling for externalizing problems (EXT) to account for the correlation between INT and EXT. We used a twin sample from Colorado (N = 2,544) to investigate phenotypic and genetic relationships between the three latent constructs, as well as potential sex differences in those relationships. We hypothesized that the relationship between RSB and INT would be stronger for females than for males, whereas the relationship between RSB and EXT would be stronger for males than for females. We used phenotypic confirmatory factor analysis and multivariate twin analyses to address research questions. Our results show significant phenotypic relationships among RSB, INT, and EXT and provide modest evidence in males for a significant association between RSB and INT that persists when controlling for EXT, a finding which we interpret with caution. Our sex differences hypothesis was not fully supported, although the direction of effects was in the direction hypothesized for the association between RSB and INT. We discuss the complexity of RSB as a phenotype and the potential implications for public health.