This book presents an evidence-based approach to patients with at least two psychiatric disorders, one of which relates to substance use. The chapters are case-based and written in an accessible style that highlights commonalities, thus making it easy to understand and apply. Co-occurring Mental Illness and Substance Use Disorders: A Guide to Diagnosis and Treatment tackles a complicated subject area with rigor and real-world expertise, improving the standard of care delivered by clinicians who work with this population as well as the lives of the many people who suffer with these co-occurring disorders.