Extending Previous cG×I Findings on 5-HTTLPR's Moderation of Intervention Effects on Adolescent Substance Misuse Initiation

A case study in developmental discontinuity: PROSPER Interventions and adolescent substance use trajectories shape young adult substance use and mental health problems

The loss of John Schulenberg reverberates across the developmental and prevention sciences. In honor of his many contributions, this paper applies his ideas of developmental continuity and discontinuity to understand the process by which PROSPER delivered universal prevention programs (delivered in Grades 6 and 7) affect young adult outcomes. Guided by these developmental models, we deconstructed adolescent substance use initiation trajectories into two discrete phases-early and late adolescence, demarcated by substance use initiation levels at the end of 9th grade. We evaluated the effects of PROSPER interventions on these phases, and in turn, the effects of adolescent substance use initiation on young adult antisocial behavior, alcohol and drug use consequences, and depression symptoms. This sample included 1,984 young adults who participated in the PROSPER intervention trial in Grade 6 (two cohorts, 2002 and 2003), followed over 8 adolescent measurement occasions (Fall and Spring of Grade 6; Spring of Grades 7-12). Young adult outcomes were averaged across three waves (collected at ages 20, 23, and 25). PROSPER interventions were associated with reduced substance use initiation in early adolescence, but not escalation during late adolescence. In turn, substance use in both early and late adolescence was uniquely associated with young adult antisocial behavior, depression symptoms, and substance use consequences. PROSPER interventions were associated with young adult antisocial behavior and problematic substance use via reduced risk for early initiation status. Findings are discussed in terms of developmental continuity and discontinuity.

A systematic review of gene-by-intervention studies of alcohol and other substance use

Alcohol and other substance use problems are common, and the efficacy of current prevention and intervention programs is limited. Genetics may contribute to differential effectiveness of psychosocial prevention and intervention programs. This paper reviews gene-by-intervention (G×I) studies of alcohol and other substance use, and implications for integrating genetics into prevention science. Systematic review yielded 17 studies for inclusion. Most studies focused on youth substance prevention, alcohol was the most common outcome, and measures of genotype were heterogeneous. All studies reported at least one significant G×I interaction. We discuss these findings in the context of the history and current state of genetics, and provide recommendations for future G×I research. These include the integration of genome-wide polygenic scores into prevention studies, broad outcome measurement, recruitment of underrepresented populations, testing mediators of G×I effects, and addressing ethical implications. Integrating genetic research into prevention science, and training researchers to work fluidly across these fields, will enhance our ability to determine the best intervention for each individual across development. With growing public interest in obtaining personalized genetic information, we anticipate that the integration of genetics and prevention science will become increasingly important as we move into the era of precision medicine.

Longitudinal Links between Adolescent and Peer Conduct Problems and Moderation by a Sensitivity Genetic Index

The most extensively studied influence on adolescent conduct problem behaviors is peers, and the literature points to genetics as one source of individual differences in peer influence. The purpose of this study was to test the hypothesis that an environmental sensitivity genetic index comprised of DRD4, 5-HTTLPR, and GABRA2 variation would moderate the association between peer and adolescent conduct problems. Latent growth modeling was applied to PROSPER project longitudinal data from adolescents and their peers. Results showed the hypothesis was supported; adolescents with more copies of putative sensitivity alleles were more strongly influenced by their peers. The interaction form was consistent with differential susceptibility in follow-up analyses. Strengths and weaknesses of genetic aggregates for sensitivity research are discussed.

Genotype-environment correlation by intervention effects underlying middle childhood peer rejection and associations with adolescent marijuana use

Aggressive behavior in middle childhood can contribute to peer rejection, subsequently increasing risk for substance use in adolescence. However, the quality of peer relationships a child experiences can be associated with his or her genetic predisposition, a genotype-environment correlation (rGE). In addition, recent evidence indicates that psychosocial preventive interventions can buffer genetic predispositions for negative behavior. The current study examined associations between polygenic risk for aggression, aggressive behavior, and peer rejection from 8.5 to 10.5 years, and the subsequent influence of peer rejection on marijuana use in adolescence (n = 515; 256 control, 259 intervention). Associations were examined separately in control and intervention groups for children of families who participated in a randomized controlled trial of the family-based preventive intervention, the Family Check-Up . Using time-varying effect modeling (TVEM), polygenic risk for aggression was associated with peer rejection from approximately age 8.50 to 9.50 in the control group but no associations were present in the intervention group. Subsequent analyses showed peer rejection mediated the association between polygenic risk for aggression and adolescent marijuana use in the control group. The role of rGEs in middle childhood peer processes and implications for preventive intervention programs for adolescent substance use are discussed.

Developmental Change in Adolescent Delinquency: Modeling Time-Varying Effects of a Preventative Intervention and GABRA2 Halpotype Linked to Alcohol Use

Better integrating human developmental factors in genomic research is part of a set of next steps for testing gene-by-environment interaction hypotheses. This study adds to this work by extending prior research using time-varying effect modeling (TVEM) to evaluate the longitudinal associations between the PROSPER preventive intervention delivery system, a GABRA2 haplotype linked to alcohol use, and their interaction on adolescent delinquency. Logistic and Poisson analyses on eight waves of data spanning ages 11 to 19 (60% female, 90% Caucasian) showed the intervention reduced delinquency from ages 13 to 16. Moreover, interaction analysis revealed that the effect of the multicomponent intervention was significantly greater for T-allele carriers of the GABRA2 SNP rs279845, but only during the 13 to 16 age period. The results are discussed in terms of adolescent delinquency normativeness, implications for preventive intervention research, and the utility of incorporating development in GxE research.

Transactions Between Substance Use Intervention, the Oxytocin Receptor (OXTR) Gene, and Peer Substance Use Predicting Youth Alcohol Use

This study investigated the oxytocin receptor (OXTR) gene's moderation of associations between exposure to a substance misuse intervention, average peer substance use, and adolescents' own alcohol use during the 9th-grade. OXTR genetic risk was measured using five single nucleotide polymorphisms (SNPs), and peer substance use was based on youths' nominated closest friends' own reports of alcohol, cigarette, and marijuana use, based on data from the PROSPER project. Regression models revealed several findings. First, low OXTR risk was linked to affiliating with friends who reported less substance use in the intervention condition but not the control condition. Second, affiliating with high substance-using friends predicted youth alcohol risk regardless of OXTR risk or intervention condition. Third, although high OXTR risk youth in the intervention condition who associated with low substance-using friends reported somewhat higher alcohol use than comparable youth in the control group, the absolute level of alcohol use among these youth was still among the lowest in the sample.