Cost-utility analysis of adjunctive psychosocial therapies in bipolar disorder.

Background: There are few economic evaluations of adjunctive psychosocial therapies for bipolar disorder.

Aims: Estimate the cost-utility of in-person psychosocial therapies for adults with bipolar disorder added to treatment as usual (TAU), from an Australian Government perspective.

Method: We developed an economic model, estimating costs in 2021 Australian dollars (A$) and outcomes using quality-adjusted life-years (QALYs) gained and disability-adjusted life-years (DALYs) averted. The model compared psychoeducation, brief psychoeducation, carer psychoeducation, cognitive-behavioural therapy (CBT) and family therapy when added to TAU (i.e. pharmacotherapy) over a year for adults (18-65 years) with bipolar disorder. The relative risk of relapse was sourced from two network meta-analyses and applied to the depressive phase in the base case. Probabilistic sensitivity analysis and one-way sensitivity analyses were conducted, assessing robustness of results.

Results: Carer psychoeducation was preferred in the base case when the willingness-to-pay (WTP) threshold is below A$1000 per QALY gained and A$1500 per DALY averted. Brief psychoeducation was preferred when WTP is between A$1000 and A$300 000 per QALY gained and A$1500 and A$450 000 per DALY averted. Family therapy was only preferred at WTP thresholds above A$300 000 per QALY gained or A$450 000 per DALY averted. In sensitivity analyses, brief psychoeducation was the preferred therapy. Psychoeducation and CBT were dominated (more costly and less effective) in base-case and sensitivity analyses.

Conclusions: Carer and brief psychoeducation were found to be the most cost-effective psychosocial therapies, supporting use as adjunctive treatments for adults with bipolar disorder and their families in Australia.