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.