This video and accompanying booklet provide an introduction to mood disorders in people with developmental disabilities. It ensures that mental health professionals have the information they need to collaborate effectively on issues of diagnosis, treatment, and support. Viewers of the video will: examine six key factors relevant to dual diagnoses - medications, physical illness, quality of life, function of behaviour, loss, and abuse; get a comprehensive discussion of diagnostic criteria, differential diagnoses, treatment options, and support measures for adults with dual diagnoses; focus on the importance of collaboration among professionals and care providers. The accompanying booklet, sold in sets of five, supplements the information in the video and includes detailed charts and tables for easy reference.