Small Group Process and Outcome Research Highlights: A 25-Year Perspective.

We summarize major research findings from the past 25 years within the larger evolution of group psychotherapy. Small group process findings are highlighted from a group-as-a-whole, interpersonal relation, subgroup, individual member characteristics, and leader perspective. Special emphasis is given to cohesion and the significant correlation between cohesion and outcome. We note that group therapy is an empirically well-supported treatment for a large number of psychiatric disorders and describe evidence supporting the outcome of various theoretical orientations. Key studies showing outcome equivalence for group and individual therapy are reviewed, followed by a high-level summary of group therapy's efficacy research for depression, bipolar, social phobia, panic disorder, obsessive compulsive, bulimia nervosa, binge-eating, substance-related, trauma-related, HIV/AIDS, breast cancer, chronic pain, schizophrenia, and borderline personality. We conclude with the promise of recent advances for moving the field forward over the next 25 years.