Randomized controlled trial of internet-delivered cognitive behaviour therapy comparing standard weekly versus optional weekly therapist support.

Internet-delivered cognitive behaviour therapy (ICBT) is effective for treating anxiety and depression. The relative benefits of offering standard weekly compared to optional weekly therapist support in conjunction with ICBT within routine care has not been examined. Patients seeking ICBT for depression and or anxiety in routine care were randomized to standard (n=92) or optional (n=88) weekly support. The optional approach resulted in therapists receiving half as many messages from (1.70 vs. 3.96) and sending half as many messages to patients (3.62 vs. 7.29). Optional Support was associated with lower completion rates (56.6% versus 82.4%), but, similar to Standard Support, resulted in large reductions on the GAD-7 (within Cohen's d≥1.08; avg. reduction ≥47%) and PHQ-9 (within Cohen's d≥0.82; avg. reduction ≥43%) at post-treatment and 3-month follow-up. Optional weekly support appears clinically effective and acceptable for many patients and may reduce costs, but safety requires monitoring given lower completion rates.