The authors concluded that individual therapy may be more effective for depression in the short-term than group therapy, but evidence was limited and the clinical relevance of treatment differences uncertain. The authors’ cautious conclusions appeared to reflect the limited evidence, but lack of reporting of review methods plus questionable data synthesis methods, mean that they should be interpreted with caution.

To compare individual versus group therapy for the treatment of adults with depression.

PubMed, PsycINFO, EMBASE and Cochrane Central Register of Controlled Trials (CENTRAL) were searched from 1966 to May 2007 for studies published in any language. Some details of the search strategy were reported. Reference lists of meta-analyses and retrieved papers were also screened. Authors of studies were contacted for details of further published or unpublished studies.

Randomised controlled trials (RCTs) that compared individual therapy with group therapy for the treatment of adult patients with a depressive disorder or an elevated level of depressive symptomatology were eligible for inclusion. The review assessed explicit measures of depression and drop-outs. Depression was also assessed at one to three months and after six months follow-up.

All of the included trials evaluated cognitive behavioural therapy, although some trials had multiple arms and evaluated other treatments. The number of treatment sessions ranged from six to 20. Groups ranged from five to 13 in size. Patients were recruited from the community, clinical settings or systematic screening. Most trials focused on adults recruited from the community; a minority of trials was in specific populations (women with postpartum depression, prisoners, and patients with multiple sclerosis). In most trials, patients had to meet diagnostic criteria for depressive disorder at a diagnostic interview; in other trials patients scored high on a self-rating depression scale. All trials used the Beck Depression Inventory (BDI) as an outcome measure, but several trials used more than one measure of depression. Most trials were set in the USA.

The authors did not state how papers were selected for the review, or how many reviewers performed the selection.

Trial validity was assessed using the independence of treatment allocation, adequacy of allocation concealment, blinding of outcome assessors and completeness of follow-up.

The authors did not state how the validity assessment was performed.

For each trial, an effect size was calculated using standardised mean differences (SMDs). Effect sizes of 0 to 0.32 were considered small. Where trials reported more than one measure of depression, a mean effect size for the trial was calculated.

The authors did not state how data were extracted for the review, or how many reviewers performed the data extraction.

Pooled effect sizes (ES) with 95% confidence intervals (CI) were calculated for measures of depression, and pooled odds ratios (OR) with 95% confidence intervals were calculated for drop-outs. Random-effects models were used. Heterogeneity was assessed using the Q and the I² statistics. The number of trials required to reduce the effect size to 0.10 was also calculated (Orwin’s fail safe N).
Subgroup and sensitivity analyses and meta-regression were used to examine the influence of the following: equivalence of treatment groups; use of Beck Depression Inventory as sole outcome measure; place of recruitment; inclusion criteria for depression; type of analysis (intention-to-treat or completer); size of group; Beck Depression Inventory at baseline; and an earlier study whose population may have overlapped with a later one.

Fifteen RCTs were included (n=673 patients). These trials provided 19 comparisons. Trial quality varied. None of the trials reported independence of treatment allocation or allocation concealment. Five trials reported blinding of outcome assessors. Drop-out rates ranged from 0 to 43%. Four trials used intention-to-treat (ITT) analyses.

Depression symptomatology: Individual therapy was associated with a small but statistically significant post-test improvement in depression compared to group therapy (ES 0.20, 95% CI 0.05 to 0.35). No significant heterogeneity was found (I²=0%). The number of trials required to reduce the effect size to 0.10 was 19. Results for subgroup and sensitivity analyses were similar. There was no significant difference between individual and group therapy at one to three months follow-up (seven comparisons) or six months follow-up (seven comparisons).

Drop-out rate: Individual therapy was associated with a statistically significant reduction in drop-out rate compared to group therapy, (OR 0.56, 95% CI 0.37 to 0.86; 19 comparisons). No significant heterogeneity was found (I²=0%).

Individual therapy may be more effective for depression in the short-term than group therapy, but evidence was limited and the clinical relevance of treatment differences uncertain.

The review question was clearly stated and inclusion criteria specified for participants, intervention and study design. Several relevant sources were searched and attempts were made to minimise publication and language bias. Methods used to select studies, assess validity and extract data were not described, so it is not known whether efforts were made to reduce reviewer errors and bias. Study validity was assessed and results were reported and taken into account when drawing conclusions.

Methods used for several of the main analyses appeared questionable, since means of effect sizes from different scales within the same trial were used in the meta-analyses. Conducting analyses which did not use equivalent interventions also appeared questionable. Although the authors did subsequently run analyses to exclude other factors, these results were not highlighted as likely to be the most reliable and appropriate.

The authors’ cautious conclusions appeared to reflect the limited evidence, but a lack of reporting of review methods plus questionable methods for data synthesis, mean that they should be interpreted with a degree of caution.

Practice: The authors did not state any implications for practice.

Research: The authors stated that before firm conclusions can be drawn about the relative efficacy of individual and group therapy for depression, research is required to determine the clinical relevance of treatment differences and the mechanisms causing change in group and individual treatments. There is also a need to examine factors such as person-centred facilitative conditions, the therapeutic alliance and group cohesion.

Not stated.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.