Unlike previous generations, today's adolescents have round-the-clock opportunities for interactions on social media. This occurs during a critical period in their development, when the brain becomes especially sensitive to social rewards and punishments. A study was designed to determine whether the frequency of adolescents' social media use is associated with longitudinal changes in functional brain development.

The study sample included 169 sixth- and seventh-grade students, ranging from 11.93 to 14.52 years of age. Participants were first asked how often they checked three social media platforms (Facebook, Instagram, and Snapchat). Participants completed the Social Incentive Delay task while undergoing functional magnetic resonance imaging to measure neural responses when anticipating receiving social rewards and avoiding social punishments. These responses were measured annually for three years.

Adolescents who were 12 years of age showed different neural patterns based on social media checking behaviors. Participants with high (habitual) checking behaviors showed hypoactivation in the left amygdala, posterior insula, ventral striatum, right amygdala, right anterior insula, and left dorsolateral prefrontal cortex in response to anticipation of social feedback. Those with low (nonhabitual) checking behaviors showed hyperactivation in these same regions, but these patterns diverged over time. Participants with high checking behaviors showed longitudinal increases in neural sensitivity in these regions, whereas those with low checking behaviors showed significant longitudinal decreases in neural sensitivity in these regions.

The authors caution that it's difficult to determine whether social media use before data collection caused these distinct neural trajectories or if preexisting differences in neural activation placed some youth at risk for habitual checking behaviors. Studies exploring the neurodevelopmental trajectories of social feedback responsiveness from an earlier age are needed.