85 in 100 feel that they are at their best in summer and worst in winter, 40 in 100 have winter blues, and 1 in 100 has winter depression. Seasonal affective disorder (SAD), or winter depression, is a mood disorder related to the change in the seasons and lack of exposure to daylight. SAD is a rare example of a psychiatric disorder with a clear, identifiable biological cause.The new edition of this award winning book brings together distinguished scientists and opinion leaders to discuss the current and anticipated developments in the study and care of SAD. Highlighting clinical diagnosis and management, this book provides a valuable resource for all whom are involved in the treatment for patients with SAD. It elucidates potential areas of research that have emerged, such as the study of the circadian pacemaker and night-time sleep structure, and how their interaction influences mood. This book helps to inform and update practice, and it is suitable for a wide range of professionals and health care settings. Readership: Psychiatrists, neurologists, clinical psychologists, nurses and other team members working in mental health care. All professionals, whether clinicians or researchers, in the field of medicine and neuroscience. Anyone who is curious enough to ask what effect the seasons, light and circadian clock have on sleep, mood and wellbeing.