Exploring the utility of transdiagnostic internet-delivered cognitive behavioral therapy for symptoms of adjustment disorder: A longitudinal observational study in a routine online care setting in Western Canada

Disorder-specific Internet-delivered cognitive behavioral therapy (ICBT) for Adjustment Disorder (AD) has shown moderate effect sizes but may lack scalability in routine care, where clients present with diverse concerns. Transdiagnostic ICBT, which targets common emotional and behavioral difficulties regardless of diagnosis, may offer a more scalable solution. This study explored the utility of a transdiagnostic ICBT course for individuals with high AD symptoms. Between June 15th, 2022, and June 19th, 2023, 585 participants (72.1% women; 83.2% White) who completed a therapist-guided, transdiagnostic ICBT course and met the inclusion criteria for the present study were included in the analysis. AD symptoms were assessed at pre-treatment, post-treatment, and 3-month follow-up using the Adjustment Disorder–New Module 8 (ADNM-8). At pre-treatment, 356 (60.9%) of participants scored above the clinical cut-off (>23) on the ADNM-8. Large within-group reductions in AD symptoms were observed from pre- to post-treatment (Cohen’s d = 1.31, 95% CI [1.13, 1.48]) and pre-treatment to follow-up ( d = 1.61, 95% CI [1.41, 1.81]). Approximately 70% of participants with high AD symptoms scored below the cut-off at post-treatment, increasing to 75% at follow-up. Treatment engagement and satisfaction were high across groups, with 76.9% completing four or more lessons and 81.5% reporting overall satisfaction. Transdiagnostic ICBT appears to be a useful and acceptable treatment for individuals with high AD symptoms. Symptom improvement was comparable to those from disorder-specific interventions. The high number of self-reported AD symptoms highlights the need for early identification and scalable treatment options in routine care. • Transdiagnostic ICBT led to large reductions in AD symptoms over time • 70% no longer met criteria for high AD symptoms after treatment • Outcomes were comparable to AD-specific ICBT interventions • High engagement and satisfaction across participants • Results support scalable ICBT for AD in routine care settings