We know that the likelihood of developing many physical diseases, such as diabetes, is determined by genes. But can abnormalities in specific genes also play a part in the development of mental disorders? And, if so, can these genes actually be identified and their discovery put to use in prevention and treatment? In Mood Genes, leading psychiatrist and biological researcher Samuel Barondes answers these questions in a way that renders a complex subject both exciting and understandable. Focusing on manic depressive illness, which affects about one percent of the population and has long been known to run in families, Barondes describes the fascinating hunt for genes-called mood genes-that influence the inherited vulnerability to severe mood disorders. He builds the compelling story of this hunt on the histories of two families riddled with manic-depression, explaining what it means to have an inherited predisposition to a severe mood disorder, how to find the mood genes that are responsible, and what will happen as mood genes are found. Not long ago, saying that a behavioral tendency was genetic was generally taken to mean that it was unchangeable. Now we know that finding genes that influence particular behavioral variations may not just be used to foretell our destinies-but also to forestall them.