Social media and smartphone use are associated with blunted striatal reward response in early adolescence

Adolescents spend unprecedented time on smartphones, raising concerns that screen time, and social media use in particular, may negatively impact developing reward circuitry in the brain—the very system critical for motivation and flexible learning. We tested whether social media and overall smartphone use are associated with altered risk-taking, neural responsivity, and mental health outcomes in early adolescence. Twenty-nine participants (ages 13-15) completed a reinforcement learning gambling task while undergoing fMRI. We fit a computational model to estimate trial-wise reward prediction errors (RPEs) during a gambling task and quantified striatal RPE sensitivity, a canonical neural signature of dopaminergic reward learning. We also measured time spent on social media applications and total daily smartphone use. Adolescents averaged nearly 6 hours of screen time per day and exhibited strong preferences for the social media apps TikTok and Snapchat. Greater social media use predicted increased gambling behavior, indicating increased reward-seeking behavior. Increased screen time and social media use were associated with blunted striatal activity, suggesting a reduced neural responsiveness to rewards. App-specific analyses indicate that these diminished striatal responses were largely driven by TikTok use. Finally, smartphone use was associated with greater anxiety, depression, and intolerance of uncertainty, which were also related to reduced striatal sensitivity. These findings provide evidence consistent with an emerging maladaptive profile that links technology exposure, mental health, and reward circuit function.