Should studies of patients undergoing coronary angiography be used to evaluate the role of behavioral risk factors for coronary heart disease?

Several studies have attempted to assess the contribution of behavioral factors to coronary heart disease by relating the Type A behavior pattern to the extent of coronary artery disease (CAD) in patients undergoing coronary angiography. Although the earlier studies gave positive results, more recent results have been negative; overall the results are confusing. These differences cannot be easily explained by differences in study design. Possible confounding factors which may limit the usefulness of such studies include biased subject selection (approximately 70% of subjects were classified as Type A, and 70% had CAD) and the effects of beta blockers. Furthermore, other studies of similar design which have attempted to relate the three major risk factors to CAD have also yielded conflicting results: an association has been demonstrated consistently with cholesterol, less consistently with smoking, and not at all with hypertension. It is argued that such studies are not well suited to investigating relationships between behavioral factors and coronary heart disease.