Relaxation therapies for asthma: a systematic review

CRD COMMENTARY: The reviewers used clear inclusion criteria in terms of the study design and participants. The criteria for outcome measures were not described, but those included appear to have been appropriate. The inclusion criteria relating to the intervention were somewhat problematic in that two of the interventions (hypnotherapy and autogenic training) were not purely relaxation techniques. It is possible that these therapies could affect asthma symptoms in ways other than promoting relaxation and would, therefore, be best reviewed separately from the pure relaxation techniques. The reviewers' search strategy appears to have been thorough, using a range of databases and information sources with no language restrictions. However, no attempt was made to look for unpublished material. Two reviewers were involved in selecting and extracting data from the studies. The included studies were quality assessed using a published checklist, and the reviewers highlighted the methodological problems associated with many of the studies. The reviewers used a narrative summary to synthesise the evidence, which was appropriate due to the heterogeneity in the design of the studies. The reviewers' conclusions and criticisms of the evidence are appropriate. However, the fact that there is a lack of evidence for the efficacy of relaxation techniques in asthma should not be taken to mean that such techniques are ineffective. The included studies were generally of a poor quality and were often underpowered to detect an effect, particularly when compared with an active (and sometimes inappropriate) control. In summary, this review highlights the lack of good quality evidence in this area and points to the need for better designed studies.