PROJECT SUMMARY/ABSTRACT Stigma adversely affects mental and physical health. Societal devaluation or mistreatment from others can lead to internalization of stigma (i.e., self-stigma) among individuals with marginalized identities or traits. Internalized stigma is robustly associated with impaired mental health and health-related quality of life (HRQOL), often to a stronger degree than are interpersonal experiences of stigma (e.g., discrimination). Experts have suggested that peer support or psychological counseling may help to reduce internalized stigma and its associated health impacts, although very few studies have investigated such interventions. Health-related stigma is an umbrella term that encompasses negative judgment, blame, avoidance, rejection, disparagement, discrimination, or dehumanization of individuals due to a health condition or disease. Such health conditions may be visible (such as obesity, skin diseases, or cancers that result in disfigurement), or concealable (such as HIV, diabetes, or chronic pain). Patients who internalize health-related stigma report avoidance of health care settings and disengagement from disease management behaviors, in addition to showing signs of physiological stress. Thus, health-related stigma compounds disease burden and threatens HRQOL beyond the direct effects of the health conditions themselves. Prior research on health-related stigma has been siloed, such that studies investigate one type of stigma, its effects, and possible solutions in isolation from stigma due to other health conditions. Consistent evidence of stigma’s harms on mental and physical health across health conditions, and shared theoretical foundations for intervention development, indicate the need for a unifying approach. An intervention that reduces internalized stigma among individuals with varying health conditions would have broad impact and would shift the paradigm of how stigma is currently addressed. The current project seeks to determine the effects of a novel, transdiagnostic, group-based counseling intervention designed to help patients cope with and to reduce the internalization of health-related stigma. An intervention and a self-report measure that were previously developed to address only one form of health- related stigma will be adapted to generalize to patients of other health conditions. After piloting, a randomized controlled trial will be conducted to test the effects of the group-based counseling intervention on internalized stigma, mental health, and HRQOL. The counseling condition (which also includes peer support) will be compared to a general peer support group and a waitlist control group. Participants will be 195 men and women who report high levels of internalized stigma due to their health condition. All study procedures will be conducted online, including assessments and treatment. Participants in the counseling and peer support groups will receive 12 weekly group sessions, followed by 2 every...