Mindfulness- and acceptance-based interventions for anxiety disorders: a systematic review and meta-analysis

Authors:
VØLLESTAD Jon, NIELSEN Morten Birkeland, NIELSEN Geir Høstmark
Journal article citation:
British Journal of Clinical Psychology, 51(3), September 2012, pp.239-260.
Publisher:
Wiley

Mindfulness and acceptance-based interventions (MABIs) are receiving increasing attention in the treatment of mental disorders. This systematic review of 19 studies examined research on MABIs for patients with diagnoses of anxiety disorders. Meta-analysis of within-group pre- to post-treatment effects yielded overall Hedges’g effect sizes of 1.08 for anxiety symptoms and 0.85 for depression symptoms. For controlled studies, overall between-group Hedges’g was 0.83 for anxiety symptoms and 0.72 for depression symptoms. No significant moderating effects were found on the variables examined, apart from an observed superiority in effect size for clinical trials on samples of patients with mixed anxiety disorders. However, differential effect sizes indicated benefits of adding specific psychotherapeutic content to mindfulness training, as well as an advantage of individual over group treatment. In conclusion, MABIs are associated with robust and substantial reductions in symptoms of anxiety and comorbid depressive symptoms. Implications for future research are discussed.

Extended abstract:
Author

VOLLESTAD Jon; NIELSEN Morten Birkeland; NIELSEN Geir Hostmark;

Title

Mindfulness- and acceptance-based interventions for anxiety disorders: a systematic review and meta-analysis.

Journal citation/publication details

British Journal of Clinical Psychology, 51(3), September 2012, pp.239-260.

Summary

Most of the 19 reports included in this systematic review were of uncontrolled studies in patients with either social anxiety disorder or generalised anxiety disorder. Substantial reductions in symptoms of anxiety and comorbid depression were associated with intervention, results from five studies also revealed moderate improvement in quality of life outcomes. Further research using randomised controlled trials in which mindfulness- and acceptance-based interventions are compared with current established treatments for anxiety disorders are required.  

Context

Mindfulness- and acceptance-based interventions, MABIs, are increasingly being recognised as useful treatments for a range of psychosocial problems from anxiety and depression, to insomnia. Prior reviews on the use of these interventions for anxiety disorders have been limited to one or other of the two types of MABIs: mindfulness-based stress reduction programmes which focus exclusively on delivering mindfulness training, and; multi-component mindfulness and acceptance interventions, such as acceptance and commitment therapy and acceptance-based behaviour therapy, which focus on cognitive therapy components. The aim of this study was to systematically review the effectiveness of both “stand-alone mindfulness interventions and multi-component acceptance-based treatments for patients with clinical levels of anxiety”.

Methods

What sources were searched?
The following electronic databases were searched from the date of inception to July 2010: Medline, ISI Web of Science, PsycINFO, and the Cochrane Library Databases. The reference lists of previous reviews and meta-analyses were hand searched for additional articles.

What search terms/strategies were used?
Searches were conducted using a combination of the terms ‘anxiety’, ‘anxiety disorders’, ‘treatment’, ‘intervention’, ‘program’ (sic), or ‘therapy’. Details of specific search strategies are not reported.

What criteria were used to decide on which studies to include?
Articles were eligible for inclusion if they reported on clinical trials of mindfulness- or acceptance-based interventions in a minimum of ten adult patients with a primary diagnosis of anxiety disorder established according to DSM-IV or ICD-10 criteria, using a structured clinical interview. Reports of studies in which anxiety was assessed only through self-report were excluded. Studies had to be published in English, German or Norwegian in peer-reviewed journals.

Who decided on their relevance and quality?
Articles were screened and duplicates were removed. The remaining abstracts were then examined by two named authors working independently. Disagreements were resolved by discussion. There is no indication that studies were assessed for quality.

How many studies were included and where were they from?
The original total of 526 titles was reduced to 436 after the removal of duplicates. A further 304 articles were excluded as they did not focus on MABIs and 111 studies were rejected for a variety of reasons that are outlined in the text. The remaining 19 interventions were included in the systematic review. Study settings are not reported.

How were the study findings combined?
Within group effect sizes for measures of anxiety and depression were calculated and expressed as Hedges g values. For studies with control groups the statistic was calculated for differences in treatment effects between intervention and control conditions. Summary statistics for pre-to post-treatment change on measures of anxiety and depression severity were obtained by combining effect size estimates across studies. Potential moderator effects were investigated using the method of Hedges and Olkin, 1985, and the calculation of the Qʙ statistic.

Findings of the review

The most frequently studied anxiety disorders were social anxiety disorder, followed by generalised anxiety disorder. Thirteen of the 19 studies were uncontrolled, the remaining studies were controlled. Twelve studies used only mindfulness-based interventions; the other studies used a combination of mindfulness- and acceptance-based therapy. In the vast majority of the studies participants were allowed to take concurrent medication.

Effect sizes for anxiety pre- to post-treatment ranged from 0.29 to 2.39 and the overall within group Hedges’ g was 1.08, indicating a large effect with intervention. Effect sizes for depression symptoms ranged from 0.43 to 1.49 and the overall Hedges’ g was 0.85, also indicating a large effect. Five studies also measured quality of life outcomes; pre- to post-treatment effect sizes ranged from 0.54 to 0.56 and the overall within-group Hedges’ g of 0.65 indicated a medium effect. The results from seven studies with a three month follow-up post-treatment indicated a small positive, but non-significant, effect on anxiety post-treatment, and no change in symptoms of depression suggesting that treatment gains were maintained.

Moderator analyses were performed for: intervention type, randomised controlled trials versus uncontrolled studies, and type of disorder. No significant moderator effects were found apart from a greater intervention effect on patients with mixed anxiety disorders, although data was available from only four studies.

Authors' conclusions

“The present study adds to a growing body of evidence indicating that MABIs are associated with decreases in a broad range of symptom measures for a variety of disorders and conditions, including anxiety and depression.”

Implications for policy or practice

None are discussed.


Subject terms:
intervention, outcomes, anxiety, depression, mindfulness;
Content type:
systematic review
Link:
Journal home page
ISSN print:
0144-6657

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