We use the method of coarsened exact matching (CEM) and general practice patient‐record data from New Zealand to estimate the impact of mood disorders on medical care costs. The CEM model exploits a discretisation of the data to identify for each patient with a mood disorder a perfect statistical twin, which allows us to control for comorbidity‐related variations in medical care costs. CEM with perfect balancing of covariates yields lower annual cost estimates of mood disorders per patient (NZ$366) than regression or conventional matching methods (between $NZ372 and $413). National government expenditures on managing mood disorders are estimated to lie between 0.06 per cent and 0.10 per cent of GDP.