This book covers a curriculum of topics for treating patients with co-occurring intellectual disabilities and mental illness, better known as dual diagnosis (DD). Though these patients represent approximately three percent of the population, they are largely underserved due to a huge gap in the literature and limited training on this topic among non-psychiatric practitioners. They are often medically fragile and have co-occurring seizure disorders and other neurologic conditions, frequently presenting to psychiatrists with behavior problems when in fact they have undiagnosed, under-diagnosed or undertreated medical conditions. A medical professional who is not trained to spot the nuanced symptoms can therefore be unprepared to work with such patients. They may misdiagnose, inappropriately prescribe medications, and fail to employ the best practices as a result. This is particularly problematic because such patients often function at significantly higher levels when accurately diagnosed and appropriately treated. Written by experts in the field, this text covers the psychiatric and medical assessment of DD patients, neurologic conditions, interviewing techniques, medications, and other topics that DD patients may present with. The book also covers a myriad of other issues surrounding DD patients that physicians often struggle with, including DD patients at the interface of the legal system, human rights concerns, tips for working with families and caregivers, and general ethical considerations. The text is specifically designed for physicians who may need quick access to information in either print or digital form. Each chapter opens with case vignettes to easily demonstrate each particular scenario and is followed up with concise, practical information. All chapters include tables that summarize the clinical pearls as well as the DSM-5 and DM-ID diagnostic criteria that is most vital to care, making this an excellent resource in both the classroom and in a treatment setting. This book offers a pathway to accurate diagnosis and treatment, leaving psychiatrists and trainees better prepared to offer the full range of mental health treatment for their dual diagnosis patients.