Seven RCTs (1,362 participants) were included in the review. All studies reported adequate allocation sequence generation, allocation concealment and intention-to-treat analysis. None of the studies blinded participants to treatment allocation.
Self-guided psychological treatment was more effective than control groups at post-test (d=0.28, 95% CI 0.14 to 0.42, NNT=6.4; seven RCTs). Evidence of significant statistical heterogeneity was low (I2=28.73%). Results remained significant at eight to 12 month follow-up (d=0.27, 95% CI 0.10 to 0.44; six RCTs), but not at four to six month follow-up.
There were no significant differences in subgroup analysis when type of outcome measure, control group and personal contact at baseline compared with no contact were considered. There were no significant changes to the results when each study was removed from the overall analyses
Post-hoc power calculation reported that there was sufficient statistical power to detect a significant pooled effect size of d=0.19. No evidence of significant publication bias was identified.