Efficacy and cost-effectiveness of intensive short-term dynamic psychotherapy for treatment resistant depression: 18-Month follow-up of the Halifax depression trial

Background: Depressed patients with chronic and complex health issues commonly relapse; therefore, examining longer-term outcomes is an important consideration. For treatment resistant depression (TRD), the post-treatment efficacy of time-limited Intensive Short-Term Dynamic Psychotherapy (ISTDP) has been demonstrated but longer-term outcomes and cost-effectiveness are unclear. Method: In this superiority trial, 60 patients referred to Community Mental Health Teams (CMHT) were randomised to 2 groups (ISTDP=30 and CMHT=30). The primary outcome was Hamilton Depression Rating scale (HAM-D) scores at 18 months. Secondary outcomes included Patient Health Questionnaire (PHQ-9) depression scores and dichotomous measure remission. A health economic evaluation examined mental health costs with quality-adjusted life years (QALYs). Results: Statistically significant treatment differences in depression previously found at 6 months favouring ISTDP were maintained at 18-month follow-up. Group differences in depression were in the moderate to large range on both the observer rated (Cohen's d = .64) and self-report measures (Cohen's d = .70). At 18 months follow-up the remission rate in ISTDP patients was 40.0%, and 23.4% had discontinued antidepressants. Health economic analysis suggests that ISTDP was more cost-effective than CMHT at 18 months. Probabilistic analysis suggests that there is a 64.5% probability of ISTDP being cost-effective at a willingness to pay for a QALY of $25,000 compared to CMHT at 18 months. Limitations: Replication of these findings is necessary in larger samples and future cost analyses should also consider indirect costs. Conclusions: ISTDP demonstrates long-term efficacy and cost-effectiveness in TRD.