Up to a point. Getting a depresison diagnosis probably saved my life. A person with undiagnosed schizophrenia could become completely nonfunctional. But I'm also seeing a trend towards giving everyone's bad habits or idiocyncracies a "diagnosis." Not every kid who acts up a little has "ADHD," not everyone with poor social skills has Asperber's, and not everyone who's a little weird has a personality disorder.