Optimizing Duration of Therapist-guided Internet-delivered Cognitive Behaviour Therapy

Depression and anxiety are common and prevalent conditions that are frequently under treated. In an attempt to increase timely and accessible psychological treatment, Internet-delivered Cognitive Behaviour Therapy (ICBT) has emerged. ICBT involves delivering therapeutic content to manage depression and or anxiety via structured online lessons. This is often combined with brief therapist guidance, for example once per week for 8 weeks via secure messaging or phone calls. Although outcomes of ICBT are very impressive, there is room for improvement in terms of completion rates and outcomes. Feedback from patients suggest that some patients would prefer longer term support or follow-up care. In this two-factorial randomized controlled trial, the investigators aim to contribute to the literature by examining whether the efficacy of ICBT is improved by offering an extended period of support to clients (from 8 weeks to 12 weeks) and being offered a booster session at 16 weeks after treatment enrollment (yes vs no). Follow-up assessments will be conducted at 8, 16 and 26 weeks after treatment enrollment. Primary outcomes are reduced anxiety and depression. Secondary outcomes include reduced panic, social anxiety, trauma, quality of life, disability, work productivity, and healthcare use.