This book provides a comprehensive account of the emotional and cognitive aspects of Parkinson's disease, derived from the neurological and psychiatric assessment of hundreds of patients by the authors. It offers a thorough survey of the published literature on the topic and readers will find a complete and helpful overview of the clinical features and treatment of Parkinson's disease, followed by discussions of associated depressive disorders, anxiety, phobias, apathy, hallucinations, delusions, and sleep disorders. The authors also discuss specific cognitive deficits and the mechanisms for these disorders, as well as the psychiatric and cognitive side effects of anti-parkinsonian medications and new surgical treatments.