Evaluating Dose Response of Cognitive Behavioural Therapy Using Outpatient Electronic Medical Record Data: An Observational Study: Évaluer la relation dose-réponse de la thérapie cognitivo-comportementale au moyen des données des DME des patients externes : Une étude d’observation

Abstract

Objective

Access to cognitive behavioural therapy (CBT) in Canada is limited by long wait times. Our objective was to determine the optimal dose of CBT sessions for patients to maximize recovery and minimize treatment time.

Method

Outpatient data from electronic medical records at a specialized mental health centre between 1 January 2017 and 31 May 2024 was used. The primary outcome was having experienced a reliable and clinically significant improvement (RCSI) in symptoms since start of treatment. Kaplan–Meier estimators were used to determine the percentile who had achieved RCSI after a given number of CBT sessions. Adjusted Cox regression determined predictors of treatment response.

Results

Among patients (n = 1,853) receiving treatment, 50% showed response in Patient Health Questionnaire-9 (PHQ-9) scores at 7 sessions of low-intensity CBT (LiCBT) and 95% showed response at 23 sessions. For high-intensity CBT (HiCBT), treatment response occurred between 14 and 36 sessions for 50–95% of patients. In Generalized Anxiety Disorder Assessment-7 (GAD-7) scores, treatment response occurred between 8 and 30 sessions in LiCBT and 15 and 37 sessions in HiCBT for 50–95% of patients. Cox regression results found that neighbourhood dependency [PHQ-9: hazard ratio (HR) (95% confidence interval (CI)) = 1.32 (1.08 to 1.63), GAD-7: HR (95% CI) = 1.36 (1.12 to 1.65)] and sex (male) [PHQ-9: HR (95% CI) = 0.83 (0.70 to 0.99), GAD-7: HR (95% CI) = 0.80 (0.66 to 0.96)] were significant predictors of non-response in HiCBT. Older age at admission was a significant predictor of non-response to LiCBT [PHQ-9: HR (95% CI = 0.99 (0.98 to 1.00), GAD-7: HR (95% CI) = 0.99 (0.98 to 1.00)].

Conclusions

There are differences in the dose and the predictors of patients’ responses to LiCBT and HiCBT. These results provide insight into potential check-in points for clinicians to assess CBT treatment plans. These results may inform treatment planning, reducing longer than necessary length of stays, allowing for more patients to access mental healthcare services.

Plain Language Summary Title

How many CBT sessions help most people feel better? A real-world study of anxiety and depression treatment

Plain Language Summary

Why was the study done? Depression and anxiety are common mental health conditions. Cognitive behavioural therapy (CBT) is an effective treatment, but therapy access is often limited by long wait times. Understanding how many therapy sessions are typically needed for improvement can help with this problem.

What did the researchers do? We looked at real-world therapy records from over 1,800 patients treated between 2017 and 2024 at an outpatient mental health clinic. We wanted to find out how many CBT sessions people needed before seeing meaningful improvements in their symptoms.

What did the researchers find? In low-intensity CBT (shorter or less frequent sessions), half of the patients saw a clear improvement in depression after 7 sessions, and nearly all improved by 23 sessions. In high-intensity CBT (longer or more frequent sessions), improvements took longer, between 14 and 36 sessions for depression. Anxiety symptoms showed similar patterns, with 8-30 sessions for most in low-intensity and 15-37 in high-intensity. Certain groups took longer to improve. Men and people from more dependent neighbourhoods took longer to respond to high-intensity CBT, while older adults took longer in low-intensity CBT.

What do the results mean? Different types of CBT require different numbers of sessions for most patients to benefit. By knowing when people are likely to improve, therapists can better plan treatment check-ins. This could reduce unnecessary sessions, shorten wait times, and allow more people to receive care.