Date

6-17-2026

Department

School of Behavioral Sciences

Degree

Doctor of Philosophy in Psychology (PhD)

Chair

Anna C. Key

Keywords

co-occurring disorders, substance use, mental health, polysubstance use, trauma, phenomenlonogy

Disciplines

Psychiatry and Psychology | Psychology

Abstract

This phenomenological study explored the lived experiences of individuals with co-occurring substance use disorders (SUD) and mental health disorders (MHD), with particular attention to the transition into polysubstance use. The purpose of the study was to understand how individuals experience and make meaning of these co-occurring conditions and the factors influencing substance use patterns. Data were collected through semi-structured interviews with participants who reported both mental health challenges and substance use histories. Thematic analysis revealed that participants experienced SUD and MHD as deeply interconnected and mutually reinforcing, often functioning within a cyclical pattern of distress and temporary relief. Substance use was frequently described as a coping mechanism for managing emotional pain, trauma, and psychological symptoms. Trauma, including childhood adversity and relational harm, emerged as a significant contributing factor to both mental health challenges and substance use behaviors. Environmental influences, social normalization, and increased tolerance contributed to the transition into polysubstance use. Participants also reported significant impacts on functioning, identity, and relationships, as well as experiences of shame and isolation. Despite these challenges, many participants identified pathways toward improvement, including therapy, medication, and supportive relationships. The findings underscore the importance of integrated, trauma-informed approaches to treatment and provide insight into the complex, lived experience of individuals navigating co-occurring disorders.

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