It has been known for many years that physical disease or damage, especially of the brain, is associated with an increased risk for psychosocial disorders. However, the understanding of the mechanisms involved in these biological risk processes, and of the marked individual differences in response, is of much more recent origin. The role of genetic factors, perinatal brain damage, sex hormones, allergy, drugs, and language disorder, are among the topics reviewed by this book's expert contributors. Papers were selected to illustrate the wide range of mechanisms involved in the development of psychosocial disorders in childhood or later life. Authors were asked to write for a multidisciplinary audience, to adopt a lifespan approach, to focus on the principles involved, and to highlight the outstanding research and clinical issues in each field.