The contributions in this book deal with basic research in psychoneuroimmunology, dysfunctions of the immune system in psychiatric disorders and the possible role of viruses in psychoneuroimmunological processes. Growing knowledge about the reciprocal relationship between psychic processes and the immune system implicates more interest of clinical psychiatrists in this field because immunological dysfunction is found in depression and schizophrenia, but also in other psychiatric syndromes like anxiety disorders. The authors of the chapters, all active researchers in the field, describe the results of their scientific work and the actual state of the art. The interdisciplinary character of this book is outlined by the broad international and disciplinary range of the authors which represent a spectrum from basic scientists like pharmacologists and immunologists up to clinical psychiatrists and neurologists. New findings regarding the role of the immune system in sleep and in headache are discussed. Special emphasis is laid on methodological pitfalls in immunological studies of psychiatric disorders. Perspectives for future therapeutical strategies are outlined.