Why Some Teens Are Vulnerable to Substance Use Disorders

Why do some adolescents who experiment with alcohol or drugs go on to develop substance use disorders while others do not? For decades, research has focused on how substance use alters the developing adolescent brain. Increasingly, however, a different question is emerging: Could differences in brain development exist before substance use begins, making some adolescents more vulnerable than others?This shift in perspective has important implications for both research and clinical practice. It may help explain why experimentation with substances is relatively common during adolescence, yet only 9.8% of individuals aged 12 years and older develop harmful patterns of use or substance use disorders (SUDs). Substance exposure alone cannot account for these differences. Instead, neurobiological predispositions appear to interact with behavioral and environmental factors long before substance use onset during adolescence. Rather than focusing solely on how drugs affect the brain, growing evidence suggests that preexisting neurodevelopmental characteristics may shape vulnerability long before the first drink, cigarette, or cannabis exposure.A Shift in ThinkingAt first glance, this idea may seem counterintuitive. Adolescence is a period of neurodevelopmental change, during which motivational and reward-related systems mature earlier than the brain networks responsible for cognitive control. Compared with children and adults, adolescents are generally more responsive to rewards, novelty, peer influence, and emotionally salient experiences. These characteristics support exploration, learning, social development, and the gradual transition toward independence. Nonetheless, these same developmental processes may also increase susceptibility to substance use and other risky behaviors in a subset of youth.Risky decision-making provides a useful framework for understanding this vulnerability. Decisions made under uncertainty require individuals to weigh potential rewards against consequences, choose a course of action, and learn from the outcomes. These processes rely on the coordinated interaction of motivational, executive, and feedback-learning systems. But when these systems function atypically, the likelihood of maladaptive behaviors may increase.What Brain Imaging Is RevealingLongitudinal neuroimaging studies are beginning to support this perspective. Differences in brain structure, functional activation, and connectivity have been identified before substance exposure, suggesting that some neural characteristics precede rather than result from substance use. In particular, the interactions among large-scale brain networks— such as salience, frontoparietal control, and default mode networks — and key regions including the nucleus accumbens, anterior insula, anterior cingulate cortex, and prefrontal cortex, appear to play important roles in evaluating risk, regulating behavior, and learning from experience. Altered activation and connectivity in these regions have been associated with a greater likelihood of initiating substance use or developing problematic patterns of use, although effect sizes remain modest and no single neural marker has sufficient predictive value for clinical use.Viewing substance use through this developmental framework also helps explain why substance use frequently co-occurs with other risky behaviors, including reckless driving, unsafe sexual behavior, and delinquency. These behaviors may not represent distinct problems but instead reflect shared neurodevelopmental mechanisms that influence reward valuation, self-regulation, and adaptive learning.Neurobiology Is Only Part of the StoryNeurobiology alone does not determine an adolescent's future. Brain-based markers are probabilistic, not deterministic, and environmental experiences continue to shape developmental trajectories. Studies have shown that factors such as family history of SUDs, parental monitoring, family functioning, peer relationships, neighborhood context, socioeconomic adversity, and exposure to violence may contribute to substance use risk.For that reason, neurobiological and psychosocial factors should be viewed as contributors to substance use risk. They interact across development, and vulnerability emerges from their combined influence. Large longitudinal cohorts, particularly the Adolescent Brain Cognitive Development study, have transformed the field by allowing researchers to examine how biological, behavioral, familial, and environmental factors interact over time. These findings reinforce the value of an integrated developmental framework.Who Is at Highest Risk?Neurodevelopmental vulnerabilities are also unlikely to be distributed evenly across adolescents. For example, youth with externalizing disorders, including attention-deficit/hyperactivity disorder, conduct disorder, and oppositional defiant disorder, consistently show higher rates of early substance use and are at increased risk of developing SUDs. Many of these adolescents show altered inhibitory control and reinforcement learning, and heightened reward sensitivity, processes that overlap with the neural systems implicated in risky decision-making. Similarly, adolescents with a family history of SUDs often display differences in brain structure and function before initiating substance use, suggesting that inherited neurobiological susceptibility may interact with developmental and environmental factors. Recognizing these higher-risk populations may help clinicians identify adolescents who could benefit most from early preventive interventions and closer monitoring.From Prediction to PreventionUltimately, the goal is not simply to determine which adolescents are most likely to develop problematic substance use, although that remains important, but to understand why vulnerability emerges and how it can be modified. By identifying the neurocognitive processes that contribute to vulnerability, researchers may be able to develop interventions that target risk before maladaptive patterns become established. If differences in future-oriented thinking, deliberation, reward valuation, self-regulation, or learning from consequences contribute to substance use risk, they may represent meaningful targets for intervention. Emerging approaches are beginning to focus on strengthening these underlying decision-making processes rather than addressing substance use alone, helping adolescents better connect present choices with future goals and consequences. The growing emphasis on prevention reflects a broader shift in adolescent substance use research from identifying who develops SUDs to understanding when vulnerability emerges and how it can be modified. Rather than waiting until harmful patterns become established, researchers and clinicians are increasingly focused on developmental mechanisms that precede substance use. This approach creates opportunities for earlier intervention during adolescence, when behavioral patterns are still forming and neural systems remain adaptable, potentially reducing the likelihood that experimentation progresses to SUDs.Paola P. Mattey Mora, PhD, MPH, is an assistant research professor of psychiatry at the Indiana University School of Medicine. Her research examines the neurobiological, behavioral, and environmental factors that contribute to risky decision-making, substance use, and psychiatric vulnerability in adolescents. Leslie A. Hulvershorn, MD, MSc, is chair of the department of psychiatry and professor of psychiatry at the Indiana University School of Medicine. A board-certified child and adolescent psychiatrist and addiction medicine specialist, her research focuses on the neurobiological basis of emotion regulation and addiction risk in youth with externalizing disorders.