Does Alcohol Initiation in Early-To-Middle Adolescence Predict Changes in Reward Motivation? Evidence of Sex Differences.

Background: Reward motivation has been cross-sectionally correlated with adolescent alcohol use, but the temporal nature of this relationship remains unclear. This project sought to determine whether adolescent alcohol initiation longitudinally predicted changes in reward motivation and behavioral inhibition from early to middle adolescence, and explored the role of adolescent sex in this prediction.

Methods: A total of 180 11- to 14-year-olds were recruited and then followed for 3 years to age 14 to 17. Participants self-reported their alcohol use at all time points. We selected participants who were alcohol-naïve at Baseline (early adolescence) and then grouped them based on whether or not they reported alcohol initiation by Year 3 (Y3: middle adolescence). Adolescents completed self-report and experimental (delay discounting) measures of reward motivation and self-report measures of behavioral inhibition at Baseline and Y3.

Results: Adolescents' alcohol initiation significantly predicted higher Y3 self-reported reward motivation on one measure. Additionally, a significant sex × alcohol initiation interaction was found predicting Y3 task-based reward motivation (delay discounting), with boys' alcohol initiation predicting increased bias toward immediate reward at Y3. There was also a sex × alcohol initiation interaction predicting behavioral inhibition, with girls' alcohol initiation predicting higher behavioral inhibition at Y3.

Conclusions: Results suggest that alcohol initiation among adolescents might precede changes in reward motivation, and the effects of alcohol on reward and behavioral inhibition may differ by adolescent sex.