This book is timely. Psychiatric genetics, which is one of the most challenging areas of medical genetics, currently offers enormous opportunities to improve the understanding of mental illness and the practice of clinical psychiatry. Phenotypic issues are, of course, important in all aspects of complex genetics, and within psychiatric genetics issues of phenotype definition and measurement are crucial. Major molecular genetic investigations using both positional and candidate approaches have been ongoing for several of the major psychiatric disorders over the last 10 or 15 years. Early successes, of …