ABSTRACT
This chapter introduces the concept of co-occurring disorders, related terms, and their prevalence. The term co-occurring typically refers to a substance use disorder co-existing with a mental health disorder; however, it also refers to the co-existence of a number of health problems or disabilities. This chapter reviews four models explaining cooccurring disorders. These include mental health disorders leading to addictive behavior, substance use leading to mental health disorders, other common risk or vulnerability factors contributing to both types of disorders, and iterative combinations of these possibilities. Effective interventions, including integrated treatment and harm reduction, are also discussed.
