Discussion
anxiety disorder, anxiety
REGRESSION, SECONDARY, RECRUITMENT, DISORDERS
Using data from an RCT opposing tCBT + TAU to TAU alone, this study aimed to identify moderators that could significantly affect the cost-effectiveness (i.e., the INB) of tCBT + TAU vs. TAU from the limited societal and health system perspectives. The probability of cost-effectiveness varied according to the number of anxiety comorbidities. tCBT + TAU had a 95% probability of being cost-effective versus TAU at a WTP=$20/AFD in those with three anxiety disorder comorbidities and 12% in those with no anxiety comorbidity. From the health system perspective, none of the interaction terms tested were significant.The results showed that the number of comorbid anxiety disorders was a significant moderator of the association between the intervention group and the nbThe current findings complement those of Norton et al. (2021), from this same trial [To our knowledge, there is a lack of literature on factors predicting change in health system and societal costs associated with health service utilization after treatment with CBT. The current findings showed an interaction between the intervention and the presence of anxiety disorder comorbidities. This suggests that comorbidities could moderate costs in CBT trials, and this finding will need further exploration.Some limitations of the study need to be considered. First, it is noteworthy that the RCT on which the present study was based was powered for the primary outcome, which was the BAI score, and not cost. A lack of power can have a more severe impact when interpreting the linear regression models at WTP=$0/AFD (i.e., ΔC), because of the skewed nature of costs. Second, although regression diagnostics were done to assess the correctness of our models, they were not validated with data-splitting to ensure its adequacy as the sample was limited. Results will need to be replicated. Third, although not extreme, regression diagnostic highlighted skewness in data, particularly at low WTP when costs have a more considerable impact on the nbAs for the generalizability of results, the following need to be considered. This study is a secondary data analysis from an RCT, carried out in a French-speaking Canadian province, for which participants were mostly white females self-reporting a favorable socioeconomic status. Future research on potential moderators affecting the cost-effectiveness of tCBT should consider a naturalistic study design factoring in contextual elements such as access to mental health care and including a more diverse sample. Also, the recruitment process was designed to represent the primary care sector in a public health system. It limits the generalization of results to other specialty and health system contexts. Moreover, the public healthcare context is to be considered when analyzing costs related to service use as most medical care and treatments are covered or partially covered, and insurance coverage may affect help-seeking behaviours [