The creator of cognitive behavioral therapy is Aaron Beck, a psychiatrist at the University of Pennsylvania. In the 1960s, Beck was practicing psychoanalysis. But he came to realize that the approach was failing to treat his depressed patients—entrenched negative thoughts prevented them from overcoming the disorder. So he developed cognitive behavior therapy, rooted in the philosophy of Albert Ellis’s rational emotive behavior therapy, to change these harmful patterns of “emotional reasoning” and spark genuine change.