A lot of clinical psychology deals with people's problems, weaknesses and perceived abnormalities. Positive psychology, however, prefers to concentrate on building up people's strengths and aims to foster qualities such as confidence, optimism and hope. A review of 51 studies, which included a total of 4,266 people, by researchers at the University of California, Riverside, looked into the effectiveness of positive psychology interventions at treating depression. The results showed that they significantly enhanced well-being and decreased depression. The treatments worked best with people who were older and highly-motivated to improve. Individual interventions worked better than group therapy and longer periods of treatment were more effective than shorter ones.
Sin, Nancy L. and Lyubomirsky, Sonja - Enhancing well-being and alleviating depressive symptoms with positive psychology interventions: a practice-friendly meta-analysis Journal of Clinical Psychology May 2009, 65(5), 467-487