Associations of treatment effects between follow-up times and between outcome domains in interventions for somatoform disorders: Review of three Cochrane reviews

Background: Interventions for somatoform disorders typically address a range of outcomes. We aimed to examine treatment effects across outcome domains and specifically assess the association, at study level, between short and long term treatment effects and between treatment effects in different outcome domains. Methods: We used data from recent systematic reviews of interventions for somatoform disorders to address three questions: We described outcome domains and measures by compiling forest plots of standardised mean difference. We examined the association of changes in outcome between short and long-term and between different outcome domains by non-parametric correlation. Results: We analysed data from 47 studies across four outcome domains: physical symptoms, health-related quality of life, depression and anxiety. Short-term and long-term treatment effects within each outcome domain were broadly similar and were correlated Reported reduction in physical symptoms was correlated with reductions in depression (rho = 0.73, p = 0.002) and anxiety (0.70, p < 0.001) and increase in quality of life (0.54, p = 0.03). Conclusion: Short term changes in outcome measures are correlated with longer term changes; outcome changes are correlated across domains independently of the type of treatment.