Is one additional phone call enough? - Effectiveness of additional human support to reduce dropout from an internet-based intervention for depressive symptoms: A randomized-controlled trial

Background Internet-Based Interventions (IBIs) are effective treatments for mental disorders, but their implementation faces challenges, particularly in addressing high dropout rates. Adding more human support or guidance might reduce treatment dropout rates in IBIs, but it may also limit scalability. Therefore, small, easy-to-implement, guidance-based add-on interventions are warranted to reduce dropout rates. This study tests if offering one additional brief phone contact reduces treatment dropout rates in an IBI for depressive symptoms with written guidance. Methods We analyze data from N = 394 individuals participating in an IBI for depression. The intervention comprises seven CBT-based modules with module-wise written semi-standardized feedback from psychotherapists (guided IBI). Previous research applying the same IBI in adults with self-reported symptoms of depression found increased dropout rates after the second module. In the study group, therapists offered an additional brief phone call after the second module (n = 206). In the control group, no additional phone calls were offered (n = 188). We present descriptive statistics regarding the intervention course for both groups. We conducted a logistic regression to examine the preventive effect of the additional phone call on treatment dropout. Results Pooled dropout rates in the study group were 30.5 % (n = 63), and in the control group 36.1 % (n = 68), with a risk difference of about 6 % points favoring the study group. The odds ratios ranged from 1.25 to 1.33, and the relative risks ranged from 1.08 to 1.10. However, all confidence intervals overlap zero, indicating that all effect estimates are statistically non-significant. Conclusion We tested a strategy of additional human contact to reduce treatment dropout rates in a guided IBI for depressive symptoms. All estimates descriptively favored the study group, but were small and non-significant. Further research is needed to determine how additional contact can be employed to reduce treatment dropout.