Depression as a risk factor for coronary heart disease—How strong is the evidence?

A critical appraisal is made of the evidence that depression is a causal risk factor for coronary heart disease. PubMed and Science Citation Index were searched for relevant papers. Forty eight papers satisfying inclusion criteria and reporting an association between a measure of depression and a coronary disease outcome were compared in terms of baseline assessment, exposure and endpoint definition, covariates measured and whether changes in, or treatment of, depression was assessed during follow-up. There was considerable variation in the definition of depression and coronary heart disease and contradictory findings are reported. Conventional risk factors for coronary heart disease were not assessed consistently or adequately. Only three of the forty-eight papers gave consideration to the time course of depression during follow-up and prior to study entry. Potentially confounding variables such as anxiety, personality traits and other psychiatric disorders were not taken into consideration in the majority of papers. Treatment of depression during the follow-up period was not mentioned in any of the papers. In light of identified methodological shortcomings and the inconsistent findings reported we suggest that there is as yet no convincing evidence that depression is an independent causal risk factor for coronary heart disease.