The fact that the average active group treatment client was better off than the untreated controls (average ES _ 0.58) provides quantitative support for group treatment as an independently efficacious treatment. The pre- to posttreatment change comparisons begin by underscoring the overall effectiveness of group therapy. Improvement did, indeed, take place, thus confirming that group therapy works.
Patients suffering from depression and eating disorders indicated more improvement than did those with other disorders ….. the results indicate that clients in homogeneous groups outperformed those in groups with mixed symptoms.
Cohesion is reliably associated (r = .25) with group outcome when outcome is defined as reduction in symptom distress or improvement in interpersonal functioning. This association was found for groups across different settings (inpatient & outpatient) and diagnostic classifications. Cohesion is most strongly involved with patient improvement in groups using an interpersonal, psychodynamic, or cognitive-behavioral orientation.