Co-occurring disorders (CODs) refers to the occurrence of both a substance use disorder (SUD) and a psychiatric disorder, such as mood disorder, anxiety disorder, obsessive-compulsive disorder, posttraumatic stress disorder, schizophrenia, eating disorder, antisocial personality disorder, and borderline personality disorder. This chapter reviews the prevalence, patterns, and effects of CODs. Next, the relationships between psychiatric disorders and SUDs, challenges for practitioners, and types and causes of psychiatric disorders are discussed. The chapter continues with the process of conducting a comprehensive and thorough assessment using the format of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). The authors also discuss the importance of conveying assessment findings to the client and/or family and concerned significant others, as well as getting the client to accept help.
