Perceptions of multiple risk factors for heart attacks.

There is increasing evidence that in some diseases such as coronary heart disease, risk factors may interact synergistically, resulting in greater likelihood of disease than would be produced by the sum of the risk factors. These two studies aimed to examine the extent to which 210 undergraduate students and 28 heart attack patients perceive risk factors to combine synergistically. Respondents read one of four vignettes, describing information about risk factors (with high and low smoking and family history), and estimated a man's likelihood of a heart attack in a hypothetical case. In both studies an interaction was found with either a family history or smoking eliciting ratings of high likelihood of heart attack, providing no evidence of synergistic models. This finding may reflect respondents' beliefs or the insensitivity of this paper-and-pencil method in detecting synergistic effects.