Improving depression and reducing cardiac events: Which is the chicken and which is the egg?

ObjectiveTo examine the assumption that depression leads to recurrent cardiac events and death in those with heart disease.MethodsConsideration of alternative perspectives and discussion of the literature.ResultsIt is not clear from studies like MIND-IT, ENRICHD or SADHART whether depression treatment improves cardiac outcomes. In these studies, recurrent cardiac events and death were recorded 6 months or more after study entry, but shorter-term cardiac outcomes (e.g., stabilization of plaque prone to rupture and thrombosis or changes in areas of myocardium prone to life-threatening arrhythmia) were not assessed. Although the prevailing view is that shorter-term improvement in depression is necessary to improve cardiovascular outcomes, the possibility that shorter-term improvement in cardiac status might result in reduced symptoms of depression has not been examined. If correct, this possibility might explain why studies have shown that patients whose depression improves also exhibit improved cardiovascular outcomes and lower mortality, even though randomization to the depression intervention in these studies had no effect.ConclusionIt is not clear whether improving depression comes first and reduced cardiac events follows or whether patients whose cardiac status improves also exhibit improvement in depression. Which is the chicken and which the egg is more than just a philosophical question, since it may affect the direction of future research in this field, and even how we approach the care of patients with heart disease and depression.