JMIR Publications

ABSTRACT

Background:

Digital-based psychological interventions (DPIs) were suggested to be effective as shown in many randomized controlled trials (RCTs) in dealing with depression in adults. However, the effects of control comparators in these DPI studies were largely overlooked and they may also have potential in terms of depression management.

Objective:

This meta-analytical study aims to provide a quantitative estimate of the within-subject effects of the control groups across different time intervals and to explore the moderating effects of control types and symptoms severity at baseline.

Methods:

A systematic literature search was conducted in late September 2021. The control conditions in 107 RCTs with a total of 11,803 adults with depressive symptoms were included in the meta-analysis.

Results:

The control conditions collectively yielded a small to moderate effect in reducing depressive symptoms within 8 weeks since baseline assessment (g=-.358, 95% CI:-.434 to -.281); The effect grew to moderate within 9 to 24 weeks (g=-.549, 95% CI:-.638 to -.460) and peaked at g=-.810 (95% CI:-.950 to -.670) between 25 to 48 weeks. The effect was maintained at a moderate-to-large range (g=-.769, 95% CI:-1.041 to -.498) beyond 48 weeks. The magnitude of reduction differs across types of control and severity of symptoms. Care as usual (CAU) is the most powerful condition among all that produced a strong effect (g=-.950, 95% CI:-1.161 to -.739) in the medium-term. The finding that waitlist controls (WL) also produced a significant symptomatic reduction in the short-term (g=-.291, 95% CI:-.478 to -.104) refuted previously suspicion of a nocebo effect. Besides, a greater reduction in the long-term (g=-1.091, 95% CI:-1.210 to -.972) was noted among participants with severe symptoms at baseline.

Conclusions:

The present study provided evidence that depressive symptoms generally reduced over time. Given different control conditions produce variate and significant levels of symptomatic reduction. Future intervention trials must adopt an RCT design and should take into account the procedures of control treatments when examining treatment efficacy. The results of WL confirmed previous findings of spontaneous recovery among people with mild-to-moderate depressive symptoms. They may adopt watchful waiting as they wait for formal digital-based psychological services in the system. Clinical Trial: CRD42021261620 (PROSPERO)