Based on decades of experience treating individuals who live with both intellectual disabilities and psychiatric disorders, this handbook clarifies the extremely complex nature of working with dual diagnosis. In-depth information about the diagnostic process, hands-on treatment considerations, and the elements of proper staff training are featured, and complicating factors in identifying appropriate psychiatric diagnoses are addressed. Exploring the problematic underreporting of psychiatric symptoms and disorders, this guide is ideal for a variety of contexts, offering innovative approaches to treatment and intervention strategies that can be immediately implemented. Additional topics covered include medical contributors to psychiatric conditions, positive behavioral supports, and transitional planning.