Editorial: Heavy Adolescent Alcohol Use: An Accelerant of Impulsivity?

It has been difficult to disentangle factors conferring vulnerability to substance use disorders (SUDs) from the consequences of substance use. Reward sensitivity and impulsivity have been identified as adolescent risk factors that confer vulnerability for later problematic substance use.^1,2 Studies also suggest, however, that substance use itself affects brain development and behavior and that some of the same risk factors that predispose youth to SUD (eg, reward sensitivity and impulsivity) may be brought on or worsened by the neurotoxicity of drugs of abuse.^3,4 Studies examining neural and behavioral correlates of SUDs commonly include youth with varying degrees of substance exposure; thus development of vulnerabilities to substance abuse are difficult to separate from the effects of substance use. In this issue of JACC, Ivanov et al.⁵ advance our field's knowledge in this area by leveraging longitudinal data from the European IMAGEN dataset (n = 2,200)⁶ in order to characterize predictors of alcohol use at age 16 as well as trajectories of impulsivity. This design allows investigation into whether alcohol drinking in adolescence may actually be related to worsening impulsivity. The authors followed a subset of the IMAGEN sample, 304 substance-naïve 14-year-olds over 2 years. Reward system function in the brain was assessed at baseline by collecting functional magnetic resonance imaging scans during a Monetary Incentive Delay (MID)⁷ task which assessed neural response to reward anticipation and outcome. Impulsivity and delay discounting, the propensity to select smaller immediate rewards versus larger, delayed rewards, were also assessed at baseline and follow-up. Linear regression was used to evaluate longitudinal associations among the frequency of alcohol use at age 16 and impulsivity, delay discounting, and reward system function at age 14. Reward system function was measured by activation in medial orbitofrontal cortex (mOFC) and ventral striatum regions of interest during the highest versus the lowest reward levels on the MID task. These regions are involved in key aspects of reward processing, including valuation of rewarding stimuli and outcomes.^8,9.