Real-world effectiveness of minimally-guided internet-delivered cognitive behavioural therapy (iCBT) versus therapist-guided CBT: a cohort study using Ontario’s linked health-administrative data

We leveraged linked, health-administrative data to compare the real-world effectiveness of Internet-delivered iCBT (online modules with minimal, asynchronous therapist support) to therapist-guided CBT (fully-synchronous, scheduled, one-on-one sessions) for depression and anxiety disorders at an outpatient clinic within a large psychiatric hospital in Ontario, Canada (Jan 2020-Aug 2021). Using Difference-in-Differences analyses, we assessed pre-post change in depression (PHQ-9) and anxiety (GAD-7) symptoms and examined mental health (MH)-related service utilization (emergency department visits, hospitalizations, outpatient visits) using Logistic and Negative Binomial regressions. Among <i>N</i> = 167 iCBT and <i>N</i> = 300 CBT participants, treatment modality was significantly associated with pre-post symptom change (<i>p</i> < 0.01), with greater reductions in CBT (-4pt PHQ-9, -3.6pt GAD-7), compared to iCBT (-2.3pt PHQ-9, + 0.4pt GAD-7). Sensitivity analyses restricting to treatment completers somewhat attenuated this finding. Both groups experienced reductions in MH-related service use, though iCBT clients were more likely to continue visiting acute (OR_adj = 2.92, 95% CI 1.29-6.64) and outpatient services (RR_adj = 1.32, 95% CI 1.03-1.69) 1-year post-treatment, adjusted for age, comorbidities, and baseline symptoms. In routine care, minimally-guided iCBT was associated with more modest symptom reductions than therapist-guided CBT. While iCBT remains a promising approach to meeting increasing MH service demands, efforts to ensure treatment adherence are likely needed to maximize its utility.