Received 3 September 2010;
revised 15 November 2010;
accepted 14 December 2010.
Abstract
Objective
The response rates and effects of being placed on a wait-list control condition are well documented in psychiatric populations.Despite the usefulness of such estimates and the frequent use of no-treatment controls in clinical trials for




The aim of the present study was to quantify the overall effect of wait-list control groups on


Methods
Studies were retrieved via a systematic review of randomised controlled trials of cognitive behaviour therapy for

Outcomes of psychometrically robust








Percentage of change and standard mean difference effect sizes were calculated using the pre and post wait period.
Results
Eleven studies involving 314 wait-list subjects with

The analysis for a waiting period of 6 to 12 weeks revealed a mean decrease in scores on


Across studies, a statically significant small mean within-group effect size was obtained (Hedges' g=.17).
The effects were moderated by methodological quality of the trial, sample characteristics (i.e., age,


Conclusion
Subjects in a



The effects of waiting are highly variable and depend on the characteristics of the sample and of the trial.
Keywords:
Tinnitus
; Meta-analysis; Placebo effects; Wait-list group; Randomised controlled trial; Benchmark


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