# Treatment Without Cost? Effects and Side Effects of an Internet-Based Intervention for Depression: Randomized Controlled Trial

## TL;DR

This study shows that an internet-based depression intervention reduces symptoms effectively, though some users report negative side effects.

## Contribution

The study is novel in systematically evaluating both positive and negative effects of an unguided internet-based depression intervention.

## Key findings

- The intervention reduced depressive symptoms with small to medium effect sizes compared to controls.
- Negative effects were reported by 22% to 68% of participants, primarily related to the program not addressing personal issues.
- No moderation effects were found, and negative effects did not impact overall treatment outcomes.

## Abstract

Internet-based interventions for depression are increasingly integrated into health care due to their effectiveness, availability, and cost-effectiveness. However, negative effects have largely been ignored.

This study aimed to evaluate both positive and negative effects of an unguided intervention.

In total, 303 participants were analyzed using mixed models for repeated measures to assess changes in depressive symptoms via Beck Depression Inventory-II (primary outcome) after 12 weeks compared to waitlist controls with care as usual. Secondary endpoints included depressive symptoms (Patient Health Questionnaire-9 [PHQ-9]), self-esteem, and quality of life. Negative effects were evaluated using the positive and negative effects of psychotherapy scale for internet-based interventions (PANEPS-I). Moderation analyses were conducted to explore influential effects on treatment outcomes.

The intervention group showed greater reduction in depressive symptoms compared to controls, with small to medium effect sizes (g=0.30‐0.42) with averaged 14 logins. Although improvements in self-esteem and quality of life were not observed in intention-to-treat analyses, the completer sample indicated higher self-esteem in the intervention group. Negative effects were reported by 22% (22/100) to 68% (66/97), with the highest rates for program-related effects (eg, not addressing personal problems). No moderation effects were identified.

The intervention effectively reduces depressive symptoms. Although negative effects were present, they did not impact treatment outcome, tentatively suggesting that overall benefits may outweigh the negative effects for users.