Pictorial warning labels reduce sharing intentions, blunt self-relevance processes elicited by social media posts promoting cannabis edibles.

The implementation of warning labels has been shown to slow the spread of harmful content on social media, but the mechanisms by which these interventions affect individuals' sharing decisions are not yet known. This study sought to establish the efficacy of these interventions and to explore the mechanisms of their influence using two parallel studies conducted within the United States: an online experiment that tested the effects of cannabis warning labels on sharing intentions (N = 1,776), and a neuroimaging study (N = 40) to examine how warning labels influenced activity in brain regions implicated in sharing decisions. Results demonstrated that warning labels paired with cannabis posts reduced intentions to share and were associated with decreased activation of brain regions associated with self-processing compared to cannabis posts alone. These results suggest that warning labels may discourage sharing by negatively influencing perceptions of self-relevance.