Table 1. Comparison of Reward-Deficiency and Incentive Sensitization models of vulnerability to the Integrative model proposed here.

Two competing models of predisposing traits to addictions hypothesize increased vs. decreased reward system responsiveness. Here we propose an integrative neurodevelopmental model that incorporates both features. In brief, high-risk individuals with externalizing traits initially express elevated incentive motivational and striatal dopamine responses to diverse emotionally salient events. Once substance use begins, these responses become increasingly focused on the drugs and drug related cues. At the same time, cues paired with the absence of drug can come to inhibit dopamine release and associated motivational states. In this way, a pre-existing vulnerability is steered toward a disproportionate preference for drugs and drug-related stimuli, setting the stage for addictions. Positive reinforcement: Increased probability that a behavior will be repeated due to presentation of a positive event. Negative reinforcement: Increased probability that a behavior will be repeated due to the removal of an aversive event. Incentive salience: the property of a cue that renders it able to elicit approach and desire. Pre-existing susceptibility: Vulnerability traits that pre-exist substance use. Prevention: Interventions that can decrease the probability that vulnerable individuals will develop substance use problems.