Behavioural and Cognitive Psychotherapy, 2005, 33, 33–44 Printed in the United Kingdom DOI: 10.1017/S1352465804001754 A Randomized Trial of Cognitive Group Therapy vs. Waiting List for Patients with Co-Morbid Psychiatric Disorders: Effect of Cognitive Group Therapy after Treatment and Six and Twelve Months Follow-Up Roger Hagen and Hans M. Nordahl Norwegian University of Science and Technology, Trondheim, Norway Lena Kristiansen Ostmarka University Hospital, Trondheim, Norway Gunnar Morken Norwegian University of Science and Technology, Trondheim, Norway Abstract. The aim of the study was to assess the effectiveness of cognitive group therapy compared to a waiting list in a sample of patients with heterogeneous non-psychotic disorders. Participants in this study were referred from either the psychiatric in- or outpatient clinic at the psychiatric university hospital in Trondheim, Norway. The patients were assessed with SCID I and SCID II, and randomized either to cognitive group therapy (n = 15) or to a waiting list (n = 17). Self-report assessments of symptoms and interpersonal difficulties were administered at the start of therapy, after termination of therapy (8 weeks), and at 6 months and 12 months follow-up. Thirty-two patients completed 8 weeks of therapy. Results showed that an 8-week program of CBGT performed better than the waiting list controls, on symptom relief at post- treatment for all patients. The effects of therapy were still upheld at 6 and 12 months follow-up. Cognitive therapy seems to be useful and effective in a group format in naturalistic clinical settings, with patients suffering from various forms of non-psychotic co-morbid psychiatric disorders. Keywords: Cognitive group therapy, co-morbid disorders, anxiety, depression. Introduction Co-morbidity of psychiatric disorders in patients is more often the rule than the exception in clinical practice. Results from a WHO-study (Sartorius, Ustun, Lecruiber and Wittchen, 1996), Reprint requests to Roger Hagen, Department of Psychology, Norwegian University of Science and Technology, 7491 Trondheim, Norway. E-mail: roger.hagen@svt.ntnu.no © 2005 British Association for Behavioural and Cognitive Psychotherapies