This project examines the social contagion of mental health symptoms in the age of social media and places it in historical context. Mass psychogenic illness, also known as mass hysteria, involves the spread of illness symptoms in a population through social means rather than through an infectious agent. Contemporary examples of rapid increases in mental health symptoms among social media communities that have been characterized by experts as mass psychogenic illness are (1) Tourette Syndrome, (2) dissociative identity (multiple personality) disorder, (3) eating disorders, and (4) rapid onset gender dysphoria. We will investigate (1) whether such cases do indeed qualify as mass psychogenic illnesses and, if so, (2) the similarities and differences between modern mass psychogenic illnesses and those of a previous era prior to social media. Given that there are several streams of ongoing research, the specific topic can be matched to the interests of the applicant.