We included randomized controlled trials that compared psychological interventions with usual care or placebo in the treatment of adult patients having unipolar depressive disorders. Psychological treatments were defined as interventions that are based on a scientific theoretical background and that use psychological techniques to reduce symptoms and improve general well-being through modifying motivational, emotional, cognitive, behavioral, or interpersonal processes. For inclusion, they needed to have been performed either as a tailored, verbal communication process between a patient (or a group of patients) and a health care professional in direct or remote (eg, telephone) contact or as a less-intense or nonguided intervention using written information material (eg, book or computer program) that the patient worked through more or less independently. Patients had to be recruited through direct referral from a general practitioner or another primary care physician not specialized in mental health care, or by systematic screening of patients in the waiting room or listed in a primary care physician’s practice. We excluded trials that recruited patients from community-based centers specializing in mental health care. Trials had to report results on at least 1 of the following outcomes: response to treatment, remission, a score on a depression scale (posttreatment or change from baseline), or study discontinuation.
Four authors (K.L., K.S., S.J., and K.M.) reviewed all trials for screening selection and extraction. In the first screening, 1 reviewer excluded clearly irrelevant records. In the second screening, 2 reviewers independently checked all remaining records (partly after obtaining full texts). The full texts of articles were obtained for all records that were considered potentially relevant or unclear, and they were assessed formally for eligibility by at least 2 reviewers independently. Disagreements were resolved by discussion.