Cognitive behaviour therapy (CBT) is a psychological treatment. It is performed by a trained therapist either one-to-one or with a group of patients. CBT aims to change relevant thoughts and beliefs. This should then lead to mood improvements. CBT depends on collaboration between the therapist and patient, and the patient plays an active role. It is used to treat a wide range of mental and physical illnesses, including anxiety, panic, eating disorders, irritable bowel syndrome, and chronic pain.

CBT is as effective as antidepressants and counselling in the acute treatment of mild to moderate depression in young or old people, and may effect more rapid improvement than antidepressants. It is unclear whether CBT is effective with severe depression. CBT is as effective as the MAOI phenelzine in the treatment of atypical depressions.

CBT may also work well in preventing relapse in patients who have had at least one episode of depression. It also reduces depression in patients who have not responded fully to antidepressants.