Long-term outcome of cognitive behaviour therapy (CBT) clinical trials in central Scotland
Authors: Durham RC, Chambers JA, Power KG, Sharp DM, Macdonald RR, Major KA, Dow MG, Gumley AI
Journal: Health Technology Assessment Volume: 9 Issue: 42
Publication date: November 2005
Long-term outcome of cognitive behaviour therapy (CBT) clinical trials in central Scotland. Health Technol Assess 2005;9(42)
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To establish the long-term outcome of participants in clinical trials of cognitive behaviour therapy (CBT) for anxiety disorders and psychosis, examining the effectiveness and cost-effectiveness associated with receiving CBT in comparison with alternative treatments.
An attempt was made to contact and interview all of the participants in eight randomised, controlled, clinical trials of CBT for anxiety disorders and two randomised, controlled, clinical trials of CBT for schizophrenia conducted between 1985 and 2001. Case note reviews of healthcare resources used in the 2 years prior to entering the trials and the 2 years prior to follow-up interview were undertaken.
Mixed rural and urban settings in five localities in central Scotland. Anxiety disorder trials were conducted mainly in primary care and included three with generalised anxiety disorder, four with panic disorder and one with post-traumatic stress disorder (PTSD). The psychosis studies (one on relapse prevention and one with chronic disorder) were conducted in secondary care.
Of the 1071 entrants to the 10 studies, 489 agreed to participate (46% of original entrants, 52% of those available to contact).
Follow-up interviews took place between 1999 and 2003, 2-14 years after the original treatment. Interviews for Trials 1-8 were conducted by a research psychologist blind to original treatment condition. Interviews for Trials 9 and 10 were conducted by community psychiatric nurses also blind to treatment condition. Case note reviews were completed following the interview.
Main outcome measures
For Trials 1-8 the main interview-based outcome measures were: Anxiety Disorders Interview Schedule-DSM-IV for diagnosis and co-morbidity, Clinical Global Severity (0-8) and the Hamilton Anxiety Rating Scale. The main patient-rated measures were: Brief Symptom Inventory, SF-36 II, Clinical Global Improvement (1-7), and the Positive and Negative Affect Scale. For Trials 9 and 10 the primary outcome measure was the interview-based Positive and Negative Syndrome Scale (PANSS).
For the anxiety disorder studies (Trials 1-8), over half of the participants (52%) had at least one diagnosis at long-term follow-up, with significant levels of co-morbidity and health status scores comparable to the lowest 10% of the general population. Only 36% reported receiving no interim treatment for anxiety over the follow-up period with 19% receiving almost constant treatment. Patients with PTSD did particularly poorly. There was a 40% real increase in healthcare costs over the two time periods, mainly due to an increase in prescribing. A close relationship was found between poor mental and physical health for those with a chronic anxiety disorder. Treatment with CBT was associated with a better long-term outcome than non-CBT in terms of overall symptom severity but not with regard to diagnostic status. The positive effects of CBT found in the original trials were eroded over longer time periods. No evidence was found for an association between more intensive therapy and more enduring effects of CBT. Long-term outcome was found to be most strongly predicted by the complexity and severity of presenting problems at the time of referral, by completion of treatment irrespective of modality and by the amount of interim treatment during the follow-up period. The quality of the therapeutic alliance, measured in two of the studies, was not related to long-term outcome but was related to short-term outcome. The cost-effectiveness analysis showed no advantages of CBT over non-CBT. The cost of providing CBT in the original trials was only a very small proportion (6.4%) of the overall costs of healthcare for this population, which are high for both physical and mental health problems. In the psychosis studies (Trials 9 and 10), outcome was generally poor with only 10% achieving a 25% reduction in total PANSS scores from pretreatment to long-term follow-up, also cost-effectiveness analysis showed no advantages of CBT over non-CBT, although healthcare costs fell over the two time periods mainly owing to a reduction in inpatient costs.
Psychological therapy services need to recognise that anxiety disorders tend to follow a chronic course and that good outcomes with CBT over the short term are no guarantee of good outcomes over the longer term. Clinicians who go beyond standard treatment protocols of about 10 sessions over a 6-month period are unlikely to bring about greater improvement. Poor outcomes over the long term are related to greater complexity and severity of presenting problems at the time of referral, failure to complete treatment irrespective of modality and the amount of interim treatment during the follow-up period. The relative gains of CBT are greater in anxiety disorders than in psychosis. Longitudinal research designs over extended periods of time (2-5 years), with large numbers of participants (500+), are required to investigate the relative importance of patient characteristics, therapeutic alliance and therapist expertise in determining the cost-effectiveness of CBT in the longer term.