The use of antidepressant drugs in patients with ischaemic heart disease (IHD) has been debated owing to scarcity of data and conflicting results regarding the effect of these drugs on mortality.

To evaluate the association between adherence to antidepressant therapy and all-cause mortality in a population-based cohort of patients with IHD.

A total of 63 437 patients with IHD who purchased antidepressants at least once during the years 2008–2011 were retrospectively followed for all-cause mortality over 4 years. Adherence was measured as a ratio between claimed and prescribed durations of medication and modelled as non-adherence (<20%), poor (20–50%), moderate (50–80%) and good (>80%). We used multivariable survival analyses adjusted for demographic and clinical variables that may affect mortality.

The moderate and good adherence groups had significantly reduced adjusted mortality hazard ratios of 0.83 (95% CI 0.78–0.88) and 0.86 (95% CI 0.82–0.90) respectively, compared with the non-adherence group.

Adherence to antidepressant pharmacotherapy is associated with reduced all-cause mortality in a population-based large sample cohort of patients with IHD. Physicians and health policy decision-makers should step up their efforts to sustain and enhance these patients' adherence to their antidepressant regimen.