The Diagnostic and Statistical Manual of Mental Disorders (DSM), often referred to as the “psychiatrist’s bible,” is used by doctors, therapists, and health insurers as a complete reference of mental illnesses. The fourth edition of the manual, published in 1994, lists more than 350 mental disorders. The increase in the number of documented mental disorders, up from 60 disorders listed in the first version of the DSM, has generated debate over whether mental illness is being too broadly defined.

Critics of the DSM-IV contend that the American Psychiatric Association, which publishes the manual, has stretched the definition of mental disorders to include behaviors demonstrated by nearly everyone. According to Stuart A. Kirk and Herb Kutchins, “Insomnia, worrying, restlessness, getting drunk, seeking approval, reacting to criticism, feeling sad and bearing grudges are all considered possible signs of mental...