[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Mental health concerns continue to be stigmatized in traditional media, in spite of -- or perhaps contributing to --high prevalence rates of mental health diagnoses globally. This has led to the World Health Organization (WHO) declaring a public health crisis. Given stigmatization in traditional media, mental health communication scholars are investigating how mental health concerns are depicted and discussed in digital and social media spaces, but this area remains underexplored. The WHO has also outlined the importance of grassroots mental health advocacy groups in addressing the public health crisis, and an understanding of such groups' social media content is imperative. Through the theoretical lenses of information and resources, social support, advocacy, and stigma management communication, case studies of two grassroots mental health advocacy groups were conducted. Analysis of 200 social media posts, interviews with 5 content creators, and interviews with 15 users of the groups' social media feeds identified five major themes: providing information and resources through peer support, using stories, encouragement and connection to provide peer support, using peer support to foster advocacy work amongst users, progressing through stigma management communication strategies from accepting to challenging, and the importance of what is left unsaid. The theoretical and practical implications of these themes are discussed in the final chapter.