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Contributors: RH had the original idea for the study, conducted the first stage of the literature search, and wrote the paper. JW and PS conducted the second stage of the search and carried out the quality assessments. FC undertook the statistical analysis.
Objective: To determine whether cognitive behaviour therapy is an effective treatment for childhood and adolescent depressive disorder.
Design: Systematic review of six randomised trials comparing the efficacy of cognitive behaviour therapy with inactive interventions in subjects aged 8 to 19 years with depressive disorder.
Main outcome measure: Remission from depressive disorder.
Results: The rate of remission from depressive disorder was higher in the therapy group (129/208; 62%) than in the comparison group (61/168; 36%). The pooled odds ratio was 3.2 (95% confidence interval 1.9 to 5.2), suggesting a significant benefit of active treatment. Most studies, however, were based on relatively mild cases of depression and were of only moderate quality.
Conclusions: Cognitive behaviour therapy may be of benefit for depressive disorder of moderate severity in children and adolescents. It cannot, however, yet be recommended for severe depression. Definitive large trials will be required to determine whether the results of this systematic review are reliable.
Depressive disorders are a common problem in child psychiatric clinics.1 These common disorders are associated with a range of adverse outcomes, including severe social impairment, long term effects on cognitive development, suicidal behaviour, and a high risk of recurrence.2 There is much literature reviewing the usefulness of tricyclic medication in childhood depression, but a systematic review found tricyclics to be of uncertain benefit.3 The results of randomised studies of selective serotonin reuptake inhibitors have been contradictory, with one positive4 and one negative result.5
There has therefore been a growing interest in psychological treatments, particularly in cognitive behaviour therapy. The results of trials of cognitive behaviour therapy in depressed young people have, however, been difficult to interpret. Although some trials have found significant benefits, the numbers have been small and the confidence intervals for the rate of improvement have been wide. In addition, the quality of the studies varied greatly. We therefore submitted the existing literature to a systematic review. We pooled the results of randomised trials to see whether cognitive behaviour therapy is superior to other conditions in the treatment of childhood and adolescent depressive disorders. We also examined whether the results were materially influenced by the quality of the reported studies.
The systematic review was restricted to studies in which one of the therapies was a recognised form of cognitive behaviour therapy as described in standard textbooks on the subject.6,7 Studies of family therapy8,9 or interpersonal psychotherapy10 were excluded.
It is important to minimise clinical heterogeneity in systematic reviews,11 and most authorities agree that in young people depressive disorder should be distinguished from depressive symptoms.12,13 Studies were therefore included in the systematic review only if they described subjects diagnosed with depressive disorder by using standardised criteria.14 The other inclusion criteria were that patients were aged between 6 and 18 years and were randomly allocated to cognitive behaviour therapy or a comparison intervention.
The search was conducted in stages. In the first stage, conducted by RH, the literature was searched with Medline (1966-97) and Psych-lit. Reference lists from reviews and book chapters were searched, and conference proceedings were reviewed. This stage suggested that there were probably enough studies suitable for inclusion in a quantitative analysis.15 In the second stage, conducted independently by JW and PS, the computer searches were repeated and all journals that had published a randomised controlled trial in this field were searched manually. When relevant, authors of published papers were approached for further details of their work. Investigators working in the specialty were contacted. The Cochrane library was also searched for randomised trials.
The search identified 22 potential comparative studies in which cognitive behaviour therapies had been used with depressed young people. Four studies were excluded because assignment to treatment was not random,16–19 one because it was an interim analysis of an ongoing study,20 and 11 because they involved children with depressive symptoms and not depressive disorder.21–31 This left six randomised trials of cognitive behaviour therapy for depressive disorder in young people.32–37 Two of the trials were conducted by the same research group32,34 but it was clear from the trial descriptions that they were based on different samples. We did not find any studies that compared cognitive behaviour therapy with medication.
Quality of the studies was assessed by using a modified version of the scheme used by Hazell and coworkers in their systematic review of the tricyclic studies.3 Their scheme was based on the method of Chalmers and colleagues.38 The cognitive behaviour therapy studies were rated independently by JW and PS and disagreements were resolved by consensus. Each of 12 features of a study was rated on a 0-3 scale, making a total possible score of 36. These features were:
To confirm that we were using the quality rating in the same way as Hazell et al, the tricyclic studies were rated again by JW and PS. Their consensus ratings strongly correlated with those of Hazell et al (r=0.92).
In all studies depressive disorder was diagnosed with operational criteria.14 Five of the six studies used the same standardised interview to establish whether these criteria were met (Puig-Antich J, Chambers W, Schedule for affective disorders and schizophrenia for school aged children, available from New York State Psychiatric Institute). In the sixth the clinician made a global judgment on the basis of an interview and the subject’s responses on standardised depression questionnaires.33 Only two studies have thus far reported follow up data,35,39 and this meta-analysis was therefore restricted to outcomes immediately after treatment. The outcome was remission from depressive disorder.
For each study we estimated the ratio of the odds of remission after cognitive behaviour therapy compared with the odds in the comparison group or groups. Confidence intervals were calculated with the Logit approximation. The pooled odds ratio was estimated with the DerSimonian Laird method,40 with a random effects model. A test of heterogeneity was performed.
Table Table11 summarises descriptive information on the studies. No study included inpatients. Cognitive behaviour therapy was compared with a heterogeneous set of comparison interventions. Most of these interventions were designed either to be inactive (such as waiting list) or to be an attention placebo (for example, relaxation training, art exercises).
Table Table22 shows the numbers without depressive disorder at the end of treatment. All studies showed positive effects in favour of cognitive behaviour therapy. In three studies the 95% confidence intervals for the odds ratio did not include 1 (figure), indicating a significant difference in favour of cognitive behaviour therapy over the comparison conditions (129/208 v 61/168). There was no significant heterogeneity across the sample (χ2=4.5; df=5; P=0.47). The pooled odds ratio was 3.2 (95% confidence interval 1.9 to 5.2), suggesting significant improvement in the cognitive behaviour therapy group over the comparison group.
The high rate of improvement in the comparison group (36%) meant, however, that for every 100 patients who were treated with cognitive behaviour therapy there were just 26 extra patients (62−36) who improved because of it. Four patients (95% confidence interval 3 to 6 patients) would therefore need to be treated with cognitive behaviour therapy to gain one additional remission above that arising from the comparison interventions.
The per protocol analysis ignored withdrawals from treatment (table (table2)2) and may therefore have exaggerated the effects of cognitive behaviour therapy. To obtain a more conservative estimate of the effect of implementing therapy we conducted an intention to treat analysis in which we assumed that all withdrawals in the cognitive behaviour therapy group did not remit and all withdrawals in the control groups remitted (that is, remission rates of 129/218 and 75/182, respectively). The pooled odds ratio was 2.2 (1.4 to 3.5).
The mean quality rating of the cognitive behaviour therapy studies was 22.7. This is similar to that in the tricyclic studies,3 in which the mean for the five studies that presented data on remission was 23.8. There was a small negative association between the quality rating and the odds ratio (rank r=−0.46; P>0.10). This was largely because the two trials with lower scores on the quality scale showed the strongest treatment effects (tables (tables11 and and2).2). The effect of cognitive behaviour therapy was still found to be significant when these trials were excluded, with remission rates in an intention to treat analysis of 105/161 in the cognitive behaviour therapy group and 69/152 in the comparison conditions. This gave an odds ratio of 2.2 (1.3 to 3.5).
The treatment of depressive disorders is an important clinical issue for child mental health teams yet little is known about the best ways of helping these children. A systematic review of the tricyclic studies suggested that tricyclics were of uncertain benefit.3 The present systematic review of cognitive behaviour therapy studies seems to show that it is a useful treatment for children and adolescents with depressive disorders. Several issues need to be borne in mind, however, in the interpretation of these results.
With only six small trials it is difficult to use techniques such as funnel plots to examine the possibility of bias. Nevertheless, the absence of studies with a negative odds ratio does raise this possibility because it would be expected that even when a treatment is effective some small trials would have negative results.41
Any systematic review can be biased by the selective publication of positive results or by the delayed publication of negative findings. At present there is no reliable method for excluding such publication biases. We did, however, make efforts to ascertain unpublished work, and indeed two of the six studies included here were unpublished at the time of the review.34,37 Bias can also occur if there is selective exclusion of subjects after randomisation. Our intention to treat analysis, however, showed that even with the most conservative estimate of the effects of selective withdrawal there was still a significant benefit of cognitive behaviour therapy.
The small negative association between study quality and the odds ratio suggests a possible bias away from negative results in the studies with lower ratings on the quality scale. This association was largely due to two studies and their removal made no material difference to the results. Nevertheless, it has to be said that the quality of the remaining trials was only moderate. Most did not give an adequate description of the randomisation procedures. In only one was an attempt made to measure and adjust for the lack of blindness of outcome assessors that often occurs in studies of psychosocial treatments.
There was no statistical evidence of heterogeneity in this meta-analysis, but power to detect heterogeneity was low because of the small number of available trials. It is likely, however, that there was some clinical heterogeneity. In three of the trials factors that predict outcome were analysed within the studies. These analyses all showed that greater severity of depression was a significant predictor of failure to remit after cognitive behaviour therapy (DA Brent et al, personal communication).42,43 The implication is that cognitive behaviour therapy may be most effective for depression of moderate severity.
It must also be borne in mind that young people admitted to the cognitive behaviour therapy trials were generally less severely impaired than those admitted to the tricyclic trials. For instance, in the cognitive behaviour therapy study of Wood et al only a quarter of subjects had endogenous depression,35 whereas in the tricyclic studies more than half the patients had endogenous features.44–46 Moreover, many of the participants in the tricyclic trials were inpatients.
The high rate of improvement among children in the comparison group also requires some comment. The comparison group consisted mainly of interventions that were designed either to be inactive or to be an attention placebo. Only one study included an active comparison intervention—family therapy.37 The finding that more than a third of depressed patients improved with these inactive interventions suggests that there is a high rate of spontaneous remission in moderately severe juvenile depression. Cognitive behaviour therapy is an expensive intervention, taking up to 16 sessions in some of the studies reviewed here. There is a strong case then for using a brief supportive intervention as the first line treatment and reserving cognitive behaviour therapy for patients who fail to respond.
This systematic review suggests that cognitive behaviour therapy may be of benefit for mild or moderate depressive disorder in young people. It was based on only six trials, however, many of which were relatively small. Definitive larger trials will therefore be required to establish whether the results of the present meta-analysis are reliable. In the meantime, the available data suggest that cognitive behaviour therapy is a promising treatment for depressed young people.
Funding: PS was supported by the MacArthur Foundation Research Network on Psychopathology and Development (1996-7). RH’s recent research on the treatment of adolescent depression has been funded by the NHS Executive North West and by the Department of Health.
Conflict of interest: None.