Abstract
Increased sharing of mental health information online has intensified public concern that social media may amplify mental health self-diagnosis rates. While much work has examined the types of mental health information available online, little attention is paid to the mechanisms governing how this information is created and consumed. Taking a cultural evolutionary perspective, we posit that social media facilitates peer-to-peer transmission of psychiatric information in novel formats and provides new motivations to transmit such information; this alters the information people see and their reactions to it. We investigate this through an adapted transmission chain paradigm where participants sequentially modify and transmit Attention-Deficit/Hyperactivity Disorder (ADHD) explanations amongst each other, allowing us to examine how self-diagnostic tendencies evolve during this process. Across four studies, we find that such transmission increases participants’ tendency to diagnose themselves, and another individual with subclinical traits, with ADHD. Participants’ tendency to recommend this other individual to seek professional help also increases. Transmission format (i.e. generating an example list versus narrative summary) and motivation (i.e. making an explanation for maximising likes versus accuracy) moderate some effects. These results indicate that peer-to-peer transmission may play a key role in determining psychiatric diagnostic trends and shaping the public understanding of mental health.