Cost-of-illness studies for bipolar disorder: systematic review of international studies

Bipolar disorder (BD) may result in a greater burden than all forms of cancer, Alzheimer's disease and epilepsy. Cost-of-illness (COI) studies provide useful information on the economic burden that BD imposes on a society. Furthermore, COI studies are pivotal sources of evidence used in economic evaluations. This study aims to give a general overview of COI studies for BD and to discuss methodological issues that might potentially influence results. This study also aims to provide recommendations to improve practice in this area, based on the review.

A search was performed to identify COI studies of BD. The following electronic databases were searched: MEDLINE, EMBASE, PsycInfo, Cochrane Database of Systematic Reviews, HMIC and openSIGLE. The primary outcome of this review was the annual cost per BD patient. A narrative assessment of key methodological issues was also included. Based on these findings, recommendations for good practice were drafted.

Fifty-four studies were included in this review. Because of the widespread methodological heterogeneity among included studies, no attempt has been made to pool results of different studies. Potential areas for methodological improvement were identified. These were: description of the disease and population, the approach to deal with comorbidities, reporting the rationale and impact for choosing different cost perspectives, and ways in which uncertainty is addressed.

This review showed that numerous COI studies have been conducted for BD since 1995. However, these studies employed varying methods, which limit the comparability of findings. The recommendations provided by this review can be used by those conducting COI studies and those critiquing them, to increase the credibility and reporting of study results.