Studies suggest a complex relationship between cognitive-behavior therapy (CBT) and pharmacotherapy for the combined treatment of mood disorders and anxiety disorders. Combined treatment for depression may have beneficial effects when applied to patients with chronic depression and in cases to prevent relapse. In bipolar disorder there is evidence for a strong effect of psychosocial treatment on the course of the disorder. In the anxiety disorders, there are some benefits in the short term, but combined treatment may limit the maintenance of treatment gains offered by CBT alone. Combined treatment should not be considered the default treatment for mood and anxiety disorders, with the possible exception of bipolar disorder. Instead, decisions whether combined treatment is worth the added cost and effort should be made in relation to the disorder under treatment, the level of severity or chronicity, and the stage of treatment (e.g., acute vs. relapse prevention).