Efficacy and Moderators of Internet-Based Interventions in Adults with Subthreshold Depression: An Individual...

Evidence on effects of Internet-based interventions to treat subthreshold depression (sD) and prevent the onset of major depression (MDD) is inconsistent.

We conducted an individual participant data meta-analysis to determine differences between intervention and control groups (IG, CG) in depressive symptom severity (DSS), treatment response, close to symptom-free status, symptom deterioration and MDD onset as well as moderators of intervention outcomes.

Randomized controlled trials were identified through systematic searches via PubMed, PsycINFO, Embase and Cochrane Library. Multilevel regression analyses were used to examine efficacy and moderators.

Seven trials (2,186 participants) were included. The IG was superior in DSS at all measurement points (posttreatment: 6-12 weeks; Hedges' g = 0.39 [95% CI: 0.25-0.53]; follow-up 1: 3-6 months; g = 0.30 [95% CI: 0.15-0.45]; follow-up 2: 12 months, g = 0.27 [95% CI: 0.07-0.47], compared with the CG. Significantly more participants in the IG than in the CG reached response and close to symptom-free status at all measurement points. A significant difference in symptom deterioration between the groups was found at the posttreatment assessment and follow-up 2. Incidence rates for MDD onset within 12 months were lower in the IG (19%) than in the CG (26%). Higher initial DSS and older age were identified as moderators of intervention effect on DSS.

Our findings provide evidence for Internet-based interventions to be a suitable low-threshold intervention to treat individuals with sD and to reduce the incidence of MDD. This might be particularly true for older people with a substantial symptom burden.