To what extent does placebo effect explain the effect of iCBT on depression? An active controlled trial of Internet-based cognitive behavioral therapy (iCBT)
Refereed conference paper presented and published in conference proceedings

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Guided Internet-based CBT is a promising treatment for depression and anxiety. However, most of these iCBT used waitlist-controlled group for comparison. One of the major disadvantages of waitlist control is the risk of nocebo effect, which leads to overestimation of the effect size of Internet-based interventions. Thus, a scientific investigation on the specific and non-specific effects in Internet-based interventions is called for. The present study examined the specific effect of iCBT against an active control group.

An iCBT platform, “Mindwork”, was developed in Hong Kong. 90 participants with diagnoses of current major depressive episode or general anxiety disorders were randomized into iCBT or active control, which is a platform introducing topics in psychology. The iCBT and active control groups are comparable in the number of words used, length of sessions, graphics, platform wireframe, and format. This randomized controlled trial is still ongoing.

The retention and adherence rates were high (78/90 [85%]; 67/78 [86%]). Using repeated measures ANOVA, participants in both groups had reduced depressive symptoms as measured by PHQ-9 (d=2.58, p ≤ 0.01), the specific effect of iCBT did not surpass time and placebo effect. However, in subgroup analysis, a significant group*time interaction effect was found among participants with moderate to severe depression (d=0.69, p ≤ 0.05). 69% in the iCBT group had clinically significant improvement at the end of the intervention. Binary logistic regression analysis revealed that participants in iCBT was significantly more likely to have clinically significant improvement (OR= 2.75, 95% CI [1.00, 7.57]) than those in the active control group.

Although participants in both the iCBT and active control had comparable reduction in depressive symptoms, iCBT is more efficacious than active control for those with moderate or severe levels of depressive symptoms. iCBT outperformed active control in clinically significant improvement. Findings point to the necessity of including active control as comparator in future randomized controlled trials of Internet-based interventions to differentiate the specific and non-specific effects.

Acknowledgements This study was funded by the Health and Medical Research Fund, Food and Health Bureau, The Government of the Hong Kong Special Administrative Region (Ref:14151961)
Acceptance Date19/04/2019
All Author(s) ListAuyeung L., Mak W. W. S.
Name of ConferenceInternational Symposium on Digital Health
Start Date of Conference29/05/2019
End Date of Conference02/06/2019
Place of ConferenceHong Kong
Country/Region of ConferenceHong Kong
LanguagesEnglish-United States

Last updated on 2021-13-01 at 12:32