BackgroundThe UK National Institute for Health and Clinical Excellence (NICE) has recommended that cost-effectiveness analysis includes the EQ–5D; however, this is often not implemented in the area of mental health.AimsTo assess the appropriateness of using the EQ–5D to measure improvements in mental health.MethodSeventy-seven participants with psychosis were rated according to the EQ–5D and seven measures of mental health at both pre- and post-intervention. To assess construct validity we compared the (pre-intervention) mean EQ–5D scores for those with milder and more severe scores, according to each of the seven measures. To assess responsiveness we estimated the mean EQ–5D change score for those who improved (post-intervention), according to each of the measures.ResultsThe mean EQ–5D score was more favourable for both those with milder scores (mean difference: 0.044 to 0.301) and for those who improved post-intervention (mean change: 0.029 to 0.117).ConclusionsThis suggests the EQ–5D should be considered for use in future cost-effectiveness studies in the area of mental health.