What causes psychiatric disorders to appear? Are they primarily the result of people s environments, or of their genes? Increasingly, we are told that research has confirmed the importance of genetic influences on psychiatric disorders such as schizophrenia, bipolar disorder, autism, and attention-deficit/hyperactivity disorder (ADHD). This timely, challenging book provides a much-needed critical appraisal of the evidence cited in support of genetic theories of psychiatric disorders, which hold that these disorders are caused by an inherited genetic predisposition in combination with environmental agents or events. In fact, the field of psychiatric genetics is approaching the crisis stage due to the continuing failure, despite years of concerted worldwide efforts, to identify genes presumed to underlie most mental disorders. The belief that such genes exist is based on studies of families, twins, and adoptees. However, the author shows that these studies provide little if any scientifically acceptable evidence in support of genetics. In fact, researchers initial "discoveries" are rarely replicated. As this becomes more understood, and as fruitless gene finding efforts continue to pile up, we may well be headed towards a paradigm shift in psychiatry away from genetic and biological explanations of mental disorders, and towards a greater understanding of how family, social, and political environments contribute to human psychological distress. Indeed, Kenneth Kendler, a leading twin researcher and psychiatric geneticist for over two decades, wrote in a 2005 edition of The American Journal of Psychiatry that the "strong, clear, and direct causal relationship implied by the concept of a gene for ... does not exist for psychiatric disorders. Although we may wish it to be true, we do not have and are not likely to ever discover genes for psychiatric illness." The author devotes individual chapters to ADHD, autism, and bipolar disorder. Looking specifically at autism, despite the near-unanimous opinion that it has an important genetic component, the evidence cited in support of this position is stunningly weak. It consists mainly of family studies, which cannot disentangle the potential influences of genes and environment, and four small methodologically flawed twin studies whose results can be explained by non-genetic factors. Not surprisingly, then, years of efforts to find "autism genes" have come up empty. This is an important book because theories based on genetic research are having a profound impact on both scientific and public thinking, as well as on social policy decisions. In addition, genetic theories influence the types of clinical treatments received by people diagnosed with psychiatric disorders. Yet, as the author demonstrates, these theories do not stand up to critical examination.