Cognitive behavioral therapy (CBT) represents that form of psychotherapy which has most research data to build on in the treatment of mood and anxiety disorders for adults. In this review we will introduce CBT and present the results of pertinent outcome research. Efficacy at the end of treatment is discussed, as well as long term effectiveness and the efficacy of combined treatment with medication and CBT. In addition, we discuss the pros and cons of group CBT compared to CBT in individual format, and comorbidity of mental disorders. According to this review CBT is efficacious for major depressive disorder, generalized anxiety disorder, panic disorder, post-traumatic stress disorder, obsessive compulsive disorder, social phobia and specific phobia. Efficacy of CBT is equal to or better than efficacy of drugs in the treatment of the above disorders, but there is less access to CBT. Longterm effectiveness of CBT appears to be good, but research on combined treatment is yet in its infancy and conclusions are premature on its place in treatment.

Table I. Summary of evidence and effect sizes for CBT

Disorder	Treatment	Efficacy data		Effect sizes*		Long term efficacy data		Combined treatment
Depression 3, 7-19	CBT	+		0.82-0.89		+		Depends on severity
	BA	+
	IPT	+
	Medication	+				-
Dysthymia 11, 20-23	CBT	+/?		1.22**		?		+
	Medication	+
Generalized anxiety disorder 3, 24-27, 48	CBT	+		0.29-3.29		+		+/?
	Medication	+				?
Panic disorder 3, 14, 28 – 35, 48	CBT	++		0.57-1.44		++		-
	Other treatments	-				-
	Medication	-/?				?
Post-traumatic stress disorder  3, 14, 36-43	CBT	+		1.34-1.70		+		?
	EMDR	+
	Medication	+/-				?
Obsessive compulsive disorder 3, 45-50	CBT	+		1.30-1.86**		+		=
	ERP	+				+
	Other treatments	-
	Medication	+				-
Social phobia 14, 48, 51-54	CBT	+		0.29-2.30		+		=/?
	Other treatments	-
	Medication	+				-
Specific phobia 14, 55-57	CBT	++		0.48-1.05		++		-/?
	Medication	-				-

Explanations for table: CBT:Cognitive behavior therapy. BA: Behavioral activation. IPT: Interpersonal therapy. ERP: Exposure-response prevention. ?: More evidence is needed. ++: treatment of choice. +: indicates positive evidence. -: indicates inadequate evidence in efficacy research, inadequate long-term effectiveness or combined treatment is not better than monotherapies (CBT or medication). =: Combined treatments are equally effective as CBT.

*: Effect size is a standardized measure for treatment effect. The comparison in this table is with waiting list and/or placebo. Cohen‘s criteria for effect sizes: 0.2 = small effect/ 0.5 = medium effect/ 0.8 = large effect.

**: Effect size is calculated pre-post but not in comparison with waiting list and/or placebo due to lack of data.