In this study, we explored the impact of group music therapy on levels of self-reported negative affect among men and women in a residential, integrated dual diagnosis treatment program. Participants had co-occurring substance use disorders (SUDs) and mental illnesses (MIs), predomi- nantly mood and anxiety disorders.Approximately 8.9 million Americans aged 18 years and older are dually diagnosed with SUDs and MIs (Substance Abuse and Mental Health Services Administration [SAMHSA], 2010). The high prevalence of co-occurring SUDs and mood and anxiety disorders, specifically, has been clearly estab- lished in clinical investigations (Merikangas, Dierker, & Szamari, 1998). One recent publication asserts that people with addictions are twice as likely as those in the general population to be diagnosed with these particular affective psychopathologies (National Institute on Drug Abuse, 2009). When compared with singular diagnoses, the combination of substance-related and mental health disorders appears to be correlated with higher frequencies of homelessness (Caton et al., 1994), incarceration (Abram & Teplin, 1991), hospitaliza- tion (Drake & Brunette, 1998), and relapse (Swofford, Kasckow, Scheller-Gilkey, & Inderbitzin, 1996), as well as poorer overall quality of life (Singh, Mattoo, Sharan, & Basu, 2005).Although the benefits of music therapy in the treatment of SUDs and various forms of MI have been singularly researched and reported, the role and efficacy of music therapy in the treatment of individuals with coexisting disorders remains comparatively under investigated-this in spite of the fact that nearly 20% of members of the American Music Therapy Association (AMTA) reportedly work with clients with psychiatric disorders (AMTA, 2010), many of whom undoubt- edly have multiple mental health diagnoses, as indicated above.The research team for the present study was comprised of a university faculty MT-BC (principal investigator) with nearly 30 years of clinical experience with adolescents and adults with MIs and two junior-level student music therapists (SMTs) from an AMTA-approved undergraduate training program. We were not considered clinical staff at the facility; rather we were viewed as faculty and student visitors who provided voluntary music therapy sessions as a service to the residents. The fourth author, a statistician, conducted the analysis of data and assisted with interpretation of the findings.Negative AffectDefinition and PrevalenceThe term affect, while variously defined in the professional psychology literature can be understood as an umbrella term for subjective experiences of a feelingful nature. Cheetham, Allen, Yucel, and Lubman (2010) define affect as relatively brief feelings that are experienced in response to a particular stimulus or situation'' (p. 623). In the course of a typical day, healthy individuals experience a multiplicity of these brief feelings (sometimes called emotions) with varying frequency, intensity, and duration. One's perception of emotions as positive or negative is dependent on the context and his or her emotional competence, defined as the ability to interpret and respond to feelings in self and others (Gross & Munoz, 1994). In this report, we use the term negative affect (NA) to refer to any brief emotion characterized by distress or displeasure (Watson, Clark, & Tellegen, 1988). Examples include anxiety, anger, sadness, shame, fear, and so forth.Researchers have confirmed that NA figures prominently in psychopathologies, including the three most commonly represented among participants in our study: anxiety, depres- sion, and SUDs. Low positive affect and high NA (both state and trait) are major distinguishing features of anxiety and depression (Tellegen, 1985). In fact, by definition, people with Generalized Anxiety Disorder experience greater frequency, intensity, and duration of negative emotions like restlessness, irritability, worry, and fear than those without this diagnosis (APA, 2013). …