Genetic and Environmental Analysis of Behavioral Risk Factors for Adolescent Drug Use in a Community Twin Sample

Abstract

W e investigated the etiology of six problem behaviors that might facilitate an understanding of behavioral pathways to substance use and abuse in adolescents. These behavioral measures, classified as Conduct Problems, Hyperactivity, School Problems, Low Self-esteem, Neuroticism, and Social Withdrawal were the result of a previously reported (Siewert et al., 2003) modification of the Drug Use Screening Inventory (DUSI; Tarter, 1990;Tarter & Hegedus, 1991). We developed these measures as interpretable components of risk for substance use and abuse in a community based sample of 633 twin pairs, who were under the legal drinking age of 21 (mean age = 15.0 years). Using multivariate analyses, model comparisons indicated that these six behavioral measures could be thought of as two heritable, and genetically distinct, dimensions of problem behavior. Two closely competing models resulted from our analyses. The best fitting model hypothesized a general genetic factor loading on all 6 behavioral measures with a second genetic factor loading on only the three internalizing behavioral measures with loadings of 0.25-0.59 and 0.26-0.44, respectively. A second model, which fit the data almost as well, hypothesized one genetic factor loading only on the externalizing behavioral measures, and a second genetic factor loading only on the internalizing behavioral measures, with a correlation between the two latent factors of 0.75. Because our analyses show that there are two genetically distinct factors influencing these six problem behaviors, we anticipate that there may be different patterns of relationship of these factors to risk for substance use, abuse, and dependence.In a previous paper (Siewert et al., 2003) we reported on the psychometric and predictive properties of subscales derived from the Drug Use Screening Inventory (DUSI; Tarter, 1990;Tarter & Hegedus, 1991). We found that these subscales may contribute to a description of behavioral components of risk for substance use and abuse in nonclinical samples of adolescents, even though the DUSI was developed for use in clinical settings. Our goal in exploring the behaviors assessed by the DUSI was to understand the behavioral pathways to substance use and abuse in adolescence. By choosing to assess behaviors that show good discriminant validity between clinical and nonclinical samples (Kirisci et al., 1995), and which have been nominated by clinicians as of particular importance in describing the syndrome of behavioral problems often comorbid with substance use disorders, we hope to focus our study of adolescent problem behaviors on those that show an especially close relationship to the risk for substance use and abuse.To develop behavioral measures that might be used as predictors of substance use and abuse within an adolescent community sample, we modified the Drug Use Screening Inventory resulting in six subscales that characterize the common behavioral problems of adolescence: Conduct Problems, Hyperactivity, Low Self-esteem, Neuroticism, Social Withdrawal, and Sch...

Genetic Influences on Vulnerability to, and Protective Factors for, Adolescent Drinking

“…In our previous report (Siewert et al, 2003), we found no significant evidence of nonadditive genetic or shared environmental influences and no significant sex differences in the etiology of the six problem behavior domains. Genetic influences on the six behavior domains could be modeled as two latent genetic factors: the first as a general genetic factor (GF) loading on all six behaviors, and a second genetic factor (IF) loading on only the three internalizing behaviors (low selfesteem, neuroticism and social withdrawal).…”

“…Summary scores were computed as unitweighted sums of the items loading on each of the six factors. These domain scores were then normalized by applying square root transformations, and regressed on age, age-squared, sex, sex-by-age, and sex-by-agesquared as previously reported (Siewert et al, 2003). All analyses were performed on the residuals.…”

“…In a subsequent study, behavioral genetic analyses indicated an underlying etiology of these six problem behavior domains which could best be explained by one general genetic factor influencing all six domains, and a second latent genetic factor influencing the three internalizing domains (Siewert et al, 2003). An alternative model postulating two genetic factors with one factor influencing the three externalizing domains and the second influencing the three internalizing domains fits almost as well, but required a correlation of .75 between the two factors.…”

“…The subjects in this study were twins who had participated in the Colorado Adolescent/Adult Twin Study (CATS; Siewert et al, 2003Siewert et al, , 2004. We selected those subjects who were younger than the legal drinking age of 21 years (M = 15.0, SD = 2.36).…”

“…The underlying etiology of the six problem behavioral domains, classified as conduct problems, hyperactivity, school problems, low self-esteem, neuroticism, and social withdrawal, was previously described (Siewert et al, 2003) as two heritable and genetically distinct dimensions of problem behavior. We took the two best-fitting models from that study (one that proposed a generalized behavior problem factor along with an internalizing behavior factor, and one that proposed an externalizing behavior factor along with an internalizing behavior factor) and extended the analyses in this study to include an index of alcohol use.…”