Influence of initial severity of depression on effectiveness of low intensity interventions: meta-analysis of individual patient data

OBJECTIVE To assess how initial severity of depression affects the benefit derived from low intensity interventions for depression. DESIGN Meta-analysis of individual patient data from 16 datasets comparing low intensity interventions with usual care. SETTING Primary care and community settings. PARTICIPANTS 2470 patients with depression. INTERVENTIONS Low intensity interventions for depression (such as guided self help by means of written materials and limited professional support, and internet delivered interventions). MAIN OUTCOME MEASURES Depression outcomes (measured with the Beck Depression Inventory or Center for Epidemiologic Studies Depression Scale), and the effect of initial depression severity on the effects of low intensity interventions. RESULTS Although patients were referred for low intensity interventions, many had moderate to severe depression at baseline. We found a significant interaction between baseline severity and treatment effect (coefficient -0.1 (95% CI -0.19 to -0.002)), suggesting that patients who are more severely depressed at baseline demonstrate larger treatment effects than those who are less severely depressed. However, the magnitude of the interaction (equivalent to an additional drop of around one point on the Beck Depression Inventory for a one standard deviation increase in initial severity) was small and may not be clinically significant. CONCLUSIONS The data suggest that patients with more severe depression at baseline show at least as much clinical benefit from low intensity interventions as less severely depressed patients and could usefully be offered these interventions as part of a stepped care model.