Elevated Reward Region Responsivity Predicts Future Substance Use Onset But Not Overweight/Obesity Onset

Background: We tested the hypotheses that adolescents who show elevated reward region responsivity are at increased risk for initial onset of overweight/obesity and substance use, which is important because there have been no such prospective tests of the reward surfeit model of these motivated behaviors. Methods: One hundred sixty-two adolescents (mean age = 15.3 +/- 1.06 years) with healthy weights (mean body mass index = 20.8 +/- 1.90) completed functional magnetic resonance imaging paradigms that assessed neural activation in response to receipt and anticipated receipt of palatable food and monetary reward; body fat and substance use were assessed at baseline and 1-year follow-up. Results: Elevated caudate (r = .31, p < .001) and putamen (r = .28, p < .001) response to monetary reward predicted substance use onset over 1-year follow-up, but reward circuitry responsivity did not predict future overweight/obesity onset. Adolescents who reported substance use versus abstinence at baseline also showed less caudate (r = -.31, p < .001) response to monetary reward. Discussion: Results show that hyper-responsivity of reward circuitry increases risk for future substance use onset, providing novel support for the reward surfeit model. Results also imply that even a limited substance use history was associated with reduced reward region responsivity, extending results from studies that compared substance-dependent individuals with healthy control subjects and suggesting that substance use downregulates reward circuitry. However, aberrant reward region responsivity did not predict initial unhealthy weight gain.