Mental depression and myocardial infarction: a systematic review.

Background The risk of myocardial infarction (MI) in patients with depressi on is likely to be increased. So is the prevalence of post-MI depression, a nd its presence may place patients with MI at increased risk of cardiac dea th. However, several recent studies were negative. Objective: In order to assess whether the association between mental depres sion and MI is consistent across studies. Methods: We meta-analyzed cohort and case-control studies studying the asso ciation between mental depression and MI. Data were collected from Medline data base. Relative risks (RRs) and 95% confidence intervals (95% CIs) were used to measure the relation between depression and MI/cardiac death. For case-control studies the relative odds ratios (ORs) were used as a surrogat e measure of the corresponding relative risks. Results: The risk of MI in depressed subjects was meta-analyzed in 9 recent ly published population-based cohort studies. The overall RR of 1.4 (95% CI s 1.3-1.6) was significantly different from 1.0 (p <0.0001). However, the r elevance of this result was minimized by publication bias and a significant test for heterogeneity (p <0.0001). Heterogeneity could not be attributed to significant across-group differences in age-groups, instruments for asse ssment, incidences of depresseds, or adjustment procedures, and so, confoun ding variables uncontrolled so far are likely to be involved. The pooled results of 10 case-control studies indicate that a large portion of post-MI patients have a depression at discharge (16.5%), and many of th em were still depressed after 6 month follow-up, Depression after MI, altho ugh not as common as with malignancies, is three times as common as it is i n otherwise healthy populations. The risk of cardiac death in post-MI patients with depression was meta-anal yzed in 4 case-control studies. The pooled OR of 1.9 (1.1-3.2, p <0.025, he terogeneity NS) suggests that post-MI depression may put patients at increa sed risk of cardiac death. This result may not be completely unbiased: the data were only partly adjusted for independent risk factors and the studies used different instruments to estimate depression. Conclusions Depression may not be as harmful as it seems, despite studies t o the contrary. At the same time, however, independent factors may contribu te to the negative association between depression and MI. The prevalence of depression after MI is 3 times that of healthy individuals. Post-MI depres sion may not be a causal factor for subsequent cardiac death but may place patients at increased risk of subsequent cardiovascular morbidity/mortality because of increased difficulty for depressed patients to improve lifestyl es and comply with health measures otherwise.