Health state utility values of high prevalence mental disorders in Australia: results from the National Survey of Mental Health and Wellbeing

Cathrine Mihalopoulos, Lidia Engel, Long Khanh-Dao Le, Anne Magnus, Meredith Harris, Mary Lou Chatterton

High prevalence mental disorders including depression, anxiety and substance use disorders are associated with high economic and disease burden. However, there is little information regarding the health state utility values of such disorders according to their clinical severity using comparable instruments across all disorders. This study reports utility values for high prevalence mental disorders using data from the 2007 Australian National Survey of Mental Health and Wellbeing (NSMHWB). Utility values were derived from the AQoL-4D and analysed by disorder classification (affective only (AD), anxiety-related only (ANX), substance use only (SUB) plus four comorbidity groups), severity level (mild, moderate, severe), symptom recency (reported in the past 30 days), and comorbidity (combination of disorders). The adjusted Wald test was applied to detect statistically significant differences of weighted means and the magnitude of difference between groups was presented as a modified Cohen's d. In total, 1526 individuals met criteria for a 12-month mental disorder. The mean utility value was 0.67 (SD = 0.27), with lower utility values associated with higher severity levels and some comorbidities. Utility values for AD, ANX and SUB were 0.64 (SD = 0.25), 0.71 (SD = 0.25) and 0.81 (SD = 0.19), respectively. No differences in utility values were observed between disorders within disorder groups. Utility values were significantly lower among people with recent symptoms (within past 30 days) than those without; when examined by diagnostic group, this pattern held for people with SUB, but not for people with ANX or AD. Health state utility values of people with high prevalence mental disorders differ significantly by severity level, number of mental health comorbidities and the recency of symptoms, which provide new insights on the burden associated with high prevalence mental disorders in Australia. The derived utility values can be used to populate future economic models.