A Cochrane review [Abstract] 1 included 15 studies with a total of 687 subjects. Study quality was poor and sample sizes were frequently small. The use of 'as needed' medications was reduced in two studies, (47 patients), by relaxation therapy (OR 4.47, 95% CI 1.22 to 16.44). There was no significant difference in FEV1 for relaxation therapy in four studies of 150 patients, (SMD -0.01, 95% CI -0.41 to 0.40). Quality of life, measured using the Asthma Quality of Life Questionnaire in two studies, (48 patients), showed a positive effect following cognitive behavioural therapy (CBT; WMD 0.71, 95% CI 0.23 to 1.19). Peak Expiratory Flow outcome data in two studies, (51 patients), indicated a significant difference in favour of bio-feedback therapy (SMD 0.66, 95% CI 0.09 to 1.23) but no significant difference following relaxation therapy (WMD 43 l/min, 95% CI -5 to 92 l/min). There was no statistically significant improvement in depression levels following relaxation therapy (SMD 0.17, 95% CI -0.25 to 0.59). The remainder of the findings between studies were conflicting. This may have been due to the different types of interventions used and the deficiencies in trial design.
Comment: The quality of evidence is downgraded by limitations in study quality, by imprecise results (limited study size for each comparison) and by inconsistency (heterogeneity in interventions and outcomes).
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