Purpose of review: The co-occurrence of mental disorders and substance use disorders (SUDs) is very common, and associated with substantial psychiatric morbidity, functional and quality of life impairments, and societal costs. However, dual disorders are often underdetected, misdiagnosed and inadequately treated in both substance abuse and mental health settings.

Recent findings: Individuals with dual or multiple disorders generally have worse clinical features and long-term outcomes than those with single disorders. However, findings can vary depending on factors such as type(s) of psychiatric disorder(s) and substance(s) involved, and whether the mental disorder is primary or secondary, or substance-induced or independent. Underdiagnosis or misdiagnosis of dual disorders may occur due, in part, to the use of measurement instruments and diagnostic approaches that have uncertain clinical utility.

Summary: Routine, thorough, and integrated screening and diagnosis of dual disorders are needed to facilitate implementation of appropriate treatment. Results suggest that forthcoming revisions to the Diagnostic and Statistical Manual of Mental Disorders and International Classification of Diseases should categorize and define mental and SUDs such that clinicians can more readily detect and diagnose all types of substance use and mental health comorbid conditions. Adoption and widespread use of appropriate screening, assessment and diagnostic instruments, and more thorough diagnostic (clinimetric) approaches are recommended.