Increasing the accessibility to internet-based cognitive behavioural therapy for depression: A single-blind...

Research shows that internet-based cognitive behavioural therapy (iCBT) is an effective treatment for depression. However, little is known about how the length of the text material in iCBT affects outcomes.

The aim of this study was to test whether a condensed iCBT version for depression would be non-inferior to the existing full-text version in reducing depressive symptoms at post-treatment. We also wanted to test non-inferiority for secondary outcomes and explore reading speed and ADHD symptoms as potential moderators.

A single-blind randomized controlled trial was conducted (N = 267) comparing two versions of guided iCBT for depression; full-text (around 60,000 words) and condensed (around 30,000 words, with the option to listen to the text). Estimated between-group effect sizes and their confidence intervals for depression, anxiety and quality of life, were compared to a pre-determined non-inferiority margin (ES = 0.4). Moderation analyses of reading speed and ADHD symptoms were conducted.

The condensed version of iCBT was non-inferior to the full-text version on post-treatment measures for depressive symptoms (95 % CI = -0.42-0.24), anxiety symptoms (95 % CI = -0.24-0.32), and quality of life (95 % CI = -0.09-0.49). Non-inferiority was inconclusive for depressive symptoms at the one-year follow-up (95 % CI = -0.60-0.47). There was no significant moderation effects of reading speed (p = 0.06) or ADHD symptoms (p = 0.11) on depressive symptoms.

These results indicate that a condensed version of iCBT for depression is as effective at treating depression as the full-text version. By shortening texts, iCBT may be made available to more people. Due to unequal dropout rates between the groups, these results are preliminary and need to be replicated.