Guided internet-based treatment for anxiety and depression in Norwegian primary care: a randomized non-inferiority effectiveness trial

Meta-analyses suggest that therapist-guided internet-based cognitive behavioural therapy (iCBT) is as effective as face-to-face CBT for anxiety and depression, yet its non-inferiority in routine primary care settings is scarcely examined. We examined the non-inferiority of the therapist-guided program “Assisted self-help” (AS-iCBT) compared to treatment as usual within the Norwegian Prompt Mental Health Care (TAU-PMHC). A pragmatic, parallel-group, randomized controlled non-inferiority trial with 1:2 (AS-iCBT: TAU-PMHC) allocation was conducted. Participants ( n = 390, 37.4% of eligible) were adults considered for PMHC admission for anxiety and/or mild to moderate depression between October 2021, and December 2023. TAU-PMHC was predominantly individual face-to-face therapy (78%). Primary outcomes were change in symptoms of depression (PHQ-9) and anxiety (GAD-7) at six months follow-up. Symptom trajectories were analysed using latent growth curve models with robust maximum likelihood estimator (MLR), employing a non-inferiority margin of d > −0.30. Both groups showed clinically significant reductions in PHQ-9 ( d w : AS-iCBT = −1.15, TAU-PMHC = -1.26) and GAD-7 (d w : AS-iCBT = −0.92, TAU-PMHC = −1.11) at 6 months follow-up. However, AS-iCBT was not non-inferior to TAU-PMHC for primary outcomes (PHQ-9: d b = −0.11 [95% CI -0.40; 0.19]; GAD-7: d b = −0.19 [95% CI -0.43; 0.04]) and several secondary outcomes. Non-inferiority was demonstrated in client-rated but not therapist-rated alliance. AS-iCBT required approximately 46% less therapist time per client than TAU-PMHC. AS-iCBT did not meet the pre-defined criteria for non-inferiority compared to usual PMHC care for most outcomes. Nevertheless, AS-iCBT showed potential as a resource-efficient treatment option, requiring less therapist time while achieving clinically significant improvements. Further research should focus on optimizing its implementation, particularly for anxiety-related conditions. • Guided iCBT was compared to usual primary care for anxiety and depression. • Both treatments gave clinically significant improvements across outcomes. • Guided iCBT was not non-inferior on primary and several secondary outcomes. • Guided iCBT required 1.8 times less therapist time. • Client-rated therapeutic alliance in guided iCBT was non-inferior to usual care.