Author ORCID Identifier

Defense Date


Document Type


Degree Name

Doctor of Philosophy


Clinical Psychology

First Advisor

Danielle Dick


Alcohol is the most commonly used substance among youth, and risky alcohol use is associated with harmful consequences such as accidents, academic consequences, and physical and emotional health problems. Alcohol use disorders are approximately 50% heritable, yet most efforts to prevent and intervene upon youth alcohol use focus only on environmental factors. Furthermore, current prevention and intervention programs tend to have modest effects and are not uniformly effective for all individuals. Gene-by-intervention (GxI) studies offer an opportunity to expand current understanding of interventions by examining whether underlying genetic risk may contribute to differential program effects. Much of the current GxI literature on alcohol and substance use outcomes is limited in scope due to reliance on candidate gene methods, focus on youth prevention samples, and lack of understanding of mediators or mechanisms through which genetics may contribute to differential intervention effects. To address these gaps in the research, the present study aimed to 1) determine if polygenic risk for externalizing problems moderated the effectiveness of an alcohol intervention, and 2) to examine whether peer deviance and drinking motives mediated intervention effects for those at greater genetic risk. To explore whether findings were consistent across different types of interventions and developmental timing, the present study used data from two samples: a college prevention intervention program conducted with a genetically informed sample (Spit for Science; S4S), and a middle school-based prevention program targeting adolescent problem behavior with longitudinal follow up and genetic data (Project Alliance; PAL). In the S4S sample, multilevel growth curve analyses showed no evidence of interactions between polygenic risk for externalizing problems (EXT PRS) and the intervention on alcohol consumption and alcohol use disorder (AUD) symptoms across time; however, there was evidence of short-term GxI effects on AUD symptoms in post-hoc analyses. Individuals with lower EXT PRS in the intervention condition reported significantly greater reduction in AUD symptoms than individuals with higher EXT PRS and control. In the PAL sample, we observed no significant GxI effects on trajectories of alcohol consumption across time or AD symptoms. There was also no evidence of mediation via peer deviance or drinking motives in either sample. Due to limitations of statistical power, the lack of replication across studies, and the possibility of measurement error, the significant GxI effects in S4S are viewed conservatively. Larger, more well-powered studies in diverse samples are needed to explore the presence or absence of very small (f2 = .005) GxI effects and determine whether genetics can be harnessed to develop novel interventions to better address alcohol-related problems. Opportunities for attaining larger, more diverse samples are discussed.


© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission