Cognitive behavioural therapy (CBT) is now the dominant form of psychotherapy and is being used in severe mental illnesses such as schizophrenia, major depression and bipolar disorder that have traditionally been treated primarily with drugs. A team of researchers from the U.K. and Spain - none of whom declared any connections to the drug industry - reviewed a number of studies into the effectiveness of using CBT to treat schizophrenia, major depression and bipolar disorder. They found that CBT was not effective in reducing symptoms in schizophrenia or preventing relapse. It had a small effect in treating major depression but was not effective at preventing relapse in bipolar disorder.
Lynch, D., Laws, K.R. and McKenna, P.J. - Cognitive behavioural therapy for major psychiatric disorder: does it really work? A meta-analytical review of well-controlled trials Psychological Medicine January 2010, 40(1), 9-24