Impact of internet-based cognitive behavioural therapy on workplace functioning: Evidence from a real-world national evaluation

Introduction. Depression and anxiety significantly impact labour participation and productivity, leading to adverse health and economic outcomes at a population level. Internet-based Cognitive Behavioural Therapy (iCBT) has emerged as a cost-effective intervention within workplace settings, but more generalisable evidence is lacking. This naturalistic, observational study investigated the impact of iCBT on work-related outcomes using nationally representative data from patients enrolled in routine care in Ireland. Methods. We analysed retrospective data from N=7125 patients enrolled in iCBT through the Irish national health service between March 2023-May 2024. The Work Productivity and Activity Impairment (WPAI) questionnaire was used to measure absenteeism, presenteeism, overall productivity loss, and activity impairment. Secondary outcomes included depression (Patient Health Questionnaire-9) and anxiety (Generalised Anxiety Disorder-7). We used mixed-effects models to assess pre-post treatment changes in outcomes, and estimated cost-savings from productivity improvement using Irish median salary data. Results. Overall, patients showed significant improvements in all WPAI outcomes with small effect sizes (6-9%, d=.18-30). Greater improvements in workplace functioning were linked to larger reductions in depression (r=.10-.34) and anxiety symptoms (r=.06-.33), both of which on average reduced by ~3 points. Patients with higher baseline clinical severity experienced more substantial improvements in workplace functioning than subclinical patients. These productivity gains correspond to >€4000 annual savings per patient treated, totalling to over €29 million for our nationally representative sample. Conclusion. Our findings support iCBT as a scalable, cost-effective intervention that can effectively improve workplace functioning associated with depression and anxiety when integrated within public health service provision.