The course of emotional distress and late mortality following myocardial infarction: Implications for depression screening and treatment

There is considerable evidence that symptoms of depression and anxiety following an acute myocardial infarction (MI) predict an increased risk of mortality.1–4 Depression has been recognized as a risk factor for mortality and medical morbidity in patients with heart disease by the American Heart Association and the European Society of Cardiology.5,6 As these organizations have noted in their scientific statements, however, there is much that we do not know about the characteristics and parameters of depression that affect this risk. One question which has not been clearly answered is whether the long-term risk of mortality is elevated in patients who have symptoms of depression around the time of an acute MI, or only in those patients who continue to report these symptoms? In this issue of the journal, Lissǻker and colleagues7 address this question using data from the national SWEDEHEART registry of patients under the age of 75 years with a first MI.7 The authors used a single item from the European Quality of life five dimensions (EQ-5D) questionnaire to assess ‘distress’. This item asks patients to report whether they feel depressed or anxious ‘to some extent’, ‘extremely’, or not at all. The EQ-5D was administered at 2 and 12 months following the MI. ‘Persistent’ distress was defined as reporting either ‘to some extent’ or ‘extremely’ at both follow-up assessments. The study found that patients who reported emotional distress at 2 months were more likely to die during the first year after the acute event than were those who reported no distress at that time. Among the patients who were still alive after 12 months, those who had reported distress at both 2 and 12 months were at higher risk of cardiovascular and non-cardiovascular mortality in the ensuing months than were those who reported no distress on each of the two occasions. Importantly, those who reported emotional distress at 2 but not at 12 months following the MI were no more likely to die in the coming years than those who denied feeling distressed at both times. Finally, patients who reported distress only at 12 months were at higher risk of mortality, but from non-cardiovascular causes. As the authors note, the finding that persistent depression and/or anxiety is associated with a higher risk of mortality is consistent with the results of many (although not all) of the previous studies with mortality and medical morbidity as endpoints, as cited by Lissǻker et al.7 Most of those studies used standardized depression or anxiety questionnaires or diagnostic interviews, and assessed depression or anxiety at various times during follow-up. The present study adds to our knowledge by showing that patients who report distress at 2 months and survive to the 12-month follow-up continue to be at higher risk of mortality only if they continue to report distress after 12 months following the acute event. The study has many positive features, including a large sample size, relatively complete data on relevant demographic and medical variables, and well-documented endpoints. However, as is the case in most registry studies, the distress measure was probably chosen on the basis of cost, convenience and low patient burden. It does not allow us to determine the relative contributions of depression and anxiety to the increased risk of mortality, or to compare these results to those of studies that used more conventional assessments of depression and anxiety. Furthermore, although it may be likely that reporting distress at both 2 and 12 months reflects ongoing, persistent distress, without more frequent assessments we cannot be sure. For example, someone classified as having transient distress after the event may have felt distress for much of the first year but not at the 12-month assessment, whereas someone classified as having persistent distress may have been distress-free for much of the interval between assessments. In short, individual differences in temporal patterns of exposure to distress during the 12 months following the acute event were not well captured. Although they provide an incomplete picture, the results of this study and those of previous studies make it clear that single occasion screening for depression may be inadequate to identify high-risk patients or those in need of intervention. The frequency or optimal time to screen cannot be easily inferred from those studies, but a recent meta-analysis of prognostic studies found that the earlier the screening relative to the acute cardiac event, the higher the rate of false positives. Depression identified more than 2 weeks after the MI was generally a better predictor of outcomes than depression assessed within the first 2 weeks.8 Another study found that post-MI patients with significant and increasing depressive symptoms over a 12-month period were at greater risk of new cardiac events than were non-depressed patients. Patients with significant but decreasing symptoms, on the other hand, were not at increased risk compared to patients who were not depressed.9 Thus more frequent assessments may be needed to identify high-risk patients accurately over time, even after 12 months following the MI. In addition to pharmacotherapy,1 psychotherapy10 and exercise training11 may improve symptoms of depression and anxiety in patients with heart disease. To date, however, only one of the randomized clinical trials in patients with coronary heart disease found that treating depression improved event-free survival,12 but all of the major trials have found that patients whose depression improves have longer event-free survival than those who continue to report significant depression symptoms.13 Whether treating depression can improve survival in patients with coronary heart disease remains an open question. Nevertheless, timely identification of patients who are depressed or anxious could help improve cardiac outcomes. These patients may benefit from more aggressive cardiac care and secondary prevention efforts to help achieve optimal levels of those treatable risk factors that have been shown to improve survival. Finally, depression is one of the strongest predictors of non-adherence with medical treatment regimens.14,15 Knowing that a patient is depressed should alert the cardiologist that more effort may be needed to help the patient follow the prescribed treatment regimen in order to maximize the benefits of treatment. The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. The author(s) received no financial support for the research, authorship, and/or publication of this article.