In recent years, a considerable number of scientific papers have been published that evaluate the importance of depressive symptoms in acute coronary syndrome (ACS) patients.1 Evidence obtained from clinical findings showed that about 20% of patients with myocardial infarction (MI) have major depression, while subclinical depression is even more frequent.1 Studies revealed that mortality after myocardial infarction was twice as high in patients with depressive symptoms as compared to those not presenting with concurrent symptoms of depression.2 However, the relationship between depression and cardiovascular disease (CVD) is considered bidirectional. Epidemiologic evidence suggests that in addition to major depression, the presence of depressive symptoms may contribute to the development of coronary atherosclerosis thus suggesting that undiagnosed depression may be a risk factor for coronary heart disease (CHD).3 Assessment of the prognostic importance of depression was put on the agenda due to its high prevalence in post-MI patients.1 According to the Cooperative pain education and self-management (COPES) study, depression was an independent predictor of all-cause mortality 12 months following myocardial infarction (MI), after adjustments with left ventricular ejection fraction and Grace score.4 Data from a meta-analysis published in 2011 which included 29 studies with 16, 889 patients, the risk of all-cause and cardiovascular mortality was 2.25 (1.73-2.93) and 2.71 (1.68-4.36) in patients with post-MI depression, and the risk of adverse cardiac events increased by 59%.2

However, it was still unclear which type of depression was related to a nonfavorable prognosis after acute coronary events. The Prospective Registry Evaluating outcomes after Myocardial Infarction: Events and Recovery (PREMIER) study findings suggest that persistent, transient or newly-developed depressive symptoms (all types) are related to nonfavorable outcomes such as all-cause re-hospitalization or mortality 6 months post-MI.5 The Enhancing Recovery in Coronary Heart Disease (ENRICHD) study found a 5-year mortality risk was 87% in post-MI patients with major depression and 67% among those with minor depression.6 After comparing first and recurrent episodes of depression, the risk of all-cause mortality tripled in the case of the first episode of depression after MI, while in patients with recurrent depression it doubled.7 Of note, the first episode of depression was not related to the severity of the cardiovascular event and underlying clinical issues,7 suggesting that the first episode of depression is singularly prognostic in the setting of an acute cardiac event. The Danish National Registry showed that previous, recurrent and new-onset depression were associated with increased risk of mortality in post-ACS patients compared to non-depressed ones8 (Table 1). However, earlier papers propose an inverse relationship between depressive symptoms and left ventricular ejection fraction. The Myocardial Infarction and Depression-Intervention Trial (MIND-IT) study revealed that decreased left ventricular ejection fraction (LVEF) after MI was related to depression during the hospital stay as well as after 1 year from discharge.9 The Depression after Myocardial Infarction (DepreMi) study showed that incident post-MI depression was related to a 65%-76% elevated risk of future cardiovascular events in post-MI patients.10 This was explained, on the one hand, by the negative relationship between incident depression and LVEF and, on the other hand, by a 2.5-times increased risk of arrhythmic complications in post-MI patients with incident depression.11 Owing to these findings depression is being considered as a prognostic marker of mortality and adverse outcome in patients with CHD.12

Studies suggest a negative role of demographic and social factors that are responsible for depressive disorder in ACS patients. The Korean Depression in acute coronary syndrome (K-DEPACS) and Escitalopram for DEPACS Escitalopram for DEPACS (EsDEPACS) cohort studies13 found that a depressive disorder after ACS was correlated with female sex, low education, and increased heart rate. A depressive episode was associated with unemployment, positive family history of depression, and decreased LVEF.

Depression has a negative influence on the recovery process after ACS. Post-ACS patients with depressive symptoms have lower adherence to treatment.14,15 A meta-analysis conducted in 2016 showed that post-ACS depression doubled the risk of nonadherence.16 It was established that behavioral factors, such as nonhealthy habits and decreased physical activity, may contribute to a nonfavorable prognosis in post-MI patients with depression.17 The Heart and Soul study showed that decreased physical activity in post-MI patients was a mediator, linking depression with future cardiovascular events.18