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Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet]. York (UK): Centre for Reviews and Dissemination (UK); 1995-.

Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet].

Influence of initial severity of depression on effectiveness of low intensity interventions: meta-analysis of individual patient data

P Bower, E Kontopantelis, A Sutton, T Kendrick, DA Richards, S Gilbody, S Knowles, P Cuijpers, G Andersson, H Christensen, B Meyer, M Huibers, F Smit, A van Straten, L Warmerdam, M Barkham, L Bilich, K Lovell, and ET Liu.

Review published: 2013.

CRD summary

The authors concluded that people with more severe depression at baseline benefited at least as much as those with less severe depression, from low-intensity interventions. This was a well-conducted review and, despite limitations in the availability of the data, the authors' conclusions appear to be reliable.

Authors' objectives

To examine the impact of the initial severity of depression, on the benefits of a low-intensity intervention for depression.


The Cochrane Library was searched, in July 2011. The included studies from nine relevant systematic reviews were checked. Individual participant data were obtained, where possible, for eligible studies. The authors of the included studies were asked if they knew of any further trials.

Study selection

Eligible trials were of people with depression or mixed depression and anxiety (with at least half the participants having depression). Depression had to be defined by clinical or research diagnostic criteria, self assessment or a cut-off score on a depression scale. Low-intensity interventions, such as self-help books or interactive computerised interventions, had to be conducted in the community or in primary care, and include less than three hours of contact with a health care professional. They had to be reported by 2000 or later, and have a minimum of 50 participants. Trials of self-help groups were excluded.

In the included trials, the mean age ranged from 30 to 45 years, two thirds to three quarters of participants were women, and 20% to 65% of patients were university educated. Six trials had a maximum depression score, to exclude patients with severe depression. Almost all trials recruited patients in the community. Most interventions used information technology, such as computerised cognitive-behavioural therapy, the rest used bibliotherapy. Most trials included some form of support from a health care professional; some were of patient self-help alone.

It appears that two reviewers selected studies for inclusion.

Assessment of study quality

Trial quality was assessed for allocation concealment, intention-to-treat analysis, and attrition. The individual patient data were checked to ensure consistency with published data, and that the variables were correctly specified.

Two reviewers independently assessed trial quality.

Data extraction

Data were collected for each trial, from depression scales, to calculate standardised mean differences and their 95% confidence intervals. Two reviewers independently extracted the data.

Methods of synthesis

The data for all the trial participants were pooled in a one-stage mixed-effects model. Sensitivity analyses were conducted to assess the impact of varying the meta-analytic model. Heterogeneity was assessed using Ι².

Secondary analyses investigated whether the impact of baseline severity, on the treatment effect, was linear at higher severity; and the impact of whether allocation was adequately concealed. Multiple imputation was used for missing data for age and depression scores. A sensitivity analysis was conducted analysing only patients with complete data. Full details of all analyses were presented in the paper.

Publication bias was assessed in funnel plots and the Egger test.

Results of the review

Twenty-nine comparisons, from 23 trials, met the eligibility criteria (4,932 participants). There was evidence of asymmetry in the funnel plot, which suggested the potential for publication bias.

Individual patient data were available for 2,470 participants (16 comparisons; 13 trials). These trials were less likely, than the other eligible trials, to include patients with a diagnosis of depression, and to deliver the health intervention by information technology. They were more likely to be of higher quality, have a larger sample, and have lower effect estimates. Ten had adequate allocation concealment and three did not.

Low-intensity interventions were effective in reducing the mean depression score (SMD -0.42, 95% CI -0.55 to -0.29; 16 comparisons; Ι²=2.9%, 95% CI 0.5 to 15). Age, gender, intervention type, and trial quality did not appear to have an impact on the pooled estimate. There was a statistically significant interaction between baseline severity and the treatment effect (-0.1, 95% CI -0.19 to -0.002), suggesting that low-intensity interventions were slightly more effective for more severe depression, but the size of this interaction was unlikely to be of clinical significance.

There was no statistically significant evidence that the interaction differed at higher depression severity, and it was not sensitive to whether allocation concealment was adequate.

Authors' conclusions

People with more severe depression at baseline benefited at least as much as those with less severe depression, from low-intensity interventions. These could be offered as part of a stepped care model.

CRD commentary

The review question was clear and was supported by potentially reproducible inclusion criteria. The search mainly relied on nine previous systematic reviews, which should have provided adequate coverage of the published literature. Evidence of small-study effects or publication bias was found. Trial investigators were contacted, but individual patient data were available for only 55% of the eligible comparisons. Therefore, there was potential for availability bias. There was some evidence that individual patient data were less likely to be available for trials of computerised cognitive-behavioural therapy, and many of these products were commercially owned. The trial characteristics were provided, heterogeneity was assessed, and the chosen method of synthesis appears to have been appropriate.

The authors' conclusions reflected the evidence presented, and they acknowledged some potential limitations of their review, which was well conducted. Despite the potential for publication and availability bias, the authors' conclusions appear to be reliable.

Implications of the review for practice and research

Practice: The authors stated that low-intensity interventions could be routinely used, as the first step, in the treatment of depression, within a stepped care system, even for patients with severe depression.

Research: The authors stated that further investigation of the moderators of the effectiveness of low-intensity interventions should be conducted. For example, investigating the impact of patient preferences, or psychological variables, such as attitudes and aptitudes.


Funding received from the UK National Institute of Health Research.

Bibliographic details

Bower P, Kontopantelis E, Sutton A, Kendrick T, Richards DA, Gilbody S, Knowles S, Cuijpers P, Andersson G, Christensen H, Meyer B, Huibers M, Smit F, van Straten A, Warmerdam L, Barkham M, Bilich L, Lovell K, Liu ET. Influence of initial severity of depression on effectiveness of low intensity interventions: meta-analysis of individual patient data. BMJ 2013; 346: f540. [PMC free article: PMC3582703] [PubMed: 23444423]

Indexing Status

Subject indexing assigned by NLM


Adult; Depressive Disorder /psychology /therapy; Female; Great Britain; Humans; Male; Middle Aged; Psychiatric Status Rating Scales; Psychotherapy /methods; Severity of Illness Index



Database entry date


Record Status

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.

CRD has determined that this article meets the DARE scientific quality criteria for a systematic review.

Copyright © 2014 University of York.

PMID: 23444423


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