Internet-Based Cognitive Behavioral Therapy and Telephone Coaching for Anxiety in Children.

Importance: Limited data are available on the long-term effectiveness of internet-based cognitive-behavioral therapy (iCBT) for anxiety among children. Objective: To evaluate the association of an iCBT intervention with anxiety in children compared with a psychoeducation control group over 12 and 24 months. Design, Setting, and Participants: This cohort study is based on 2-year follow-up data of the randomized clinical trial Master Your Worries, which was conducted between August 2017 and January 2020. Participants were Finnish school children aged 10 to 13 years identified through population-level screening as exhibiting elevated levels of anxiety. Statistical analyses for this study were performed between June 2, 2025, and June 16, 2026. Intervention: Participants in the intervention group followed an internet-based therapy program, which comprised 10 modules, including telephone contact with a coach. The control group received psychoeducation in digital form. Main Outcomes and Measures: The primary outcome was change in participants' anxiety measured by the total score of the Screen for Child Anxiety Related Disorders-Child and Parent versions (SCARED-C/P). The secondary outcomes were changes in SCARED-C and SCARED-P subscale scores as well as scores on the Child Anxiety Impact Scale, Child Depression Inventory, and Depression Anxiety and Stress Scale-21 Items. Results: A total of 465 children (median [range] age 11, [10-13] years; 332 [71%] girls) with anxiety symptoms (SCARED total score of ≥22 at baseline) were followed up for 2 years after randomization. On the basis of a linear mixed-effects model for repeated measures, the primary outcomes (SCARED-C and SCARED-P total scores) showed statistically significant differences between the groups at both the 12-month (SCARED-C mean score in the intervention group was 4.5 [95% CI, 2.2-6.8] points higher; P < .001; Cohen d = 0.35; and SCARED-P mean score was 3.4 [95% CI, 1.8-5.1] points higher; P < .001; Cohen d = 0.36) and 24-month (SCARED-C mean score in the intervention group was 4.4 [95% CI, 1.7-7.1] points higher; P = .001; Cohen d = 0.29; and SCARED-P mean score was 2.3 [95% CI, 0.1-4.5] points higher; P = .04; Cohen d = 0.19) follow-ups. Overall, the effect size of iCBT increased from 6 months to 12 months, and these results were maintained through 24 months. Statistically significant differences favoring iCBT were also seen in anxiety symptom subgroups. For example, at 12 months, the mean change in social anxiety was 1.6 points higher in the intervention group (95% CI, 1.0-2.3; Cohen d = 0.45). No statistically significant differences were seen in parental mental health. Conclusions and Relevance: In this cohort study of guided iCBT, the outcomes of the intervention extended through 24 months. This suggests a delayed increase in the effectiveness of the iCBT targeting childhood anxiety, which has important implications for future research and clinical practice.