When one's main effect is another's error: material vs. psychosocial explanations of health disparities. A commentary on Macleod et al., "is subjective social status a more important determinant of health than objective social status? Evidence from a prospective observational study of Scottish men" (61(9), 2005, 1916-1929).

Two pathways by which socioeconomic factors result in health disparities are the material and the psychosocial. Recently, Macleod and colleagues reported on data showing that a subjective measure of workplace status was not as strongly related to mortality as were objective indicators and that another psychosocial measure, perceived stress, did not mediate the impact of these indicators [Macleod et al., 2005. Is subjective social status a more important determinant of health than objective social status? Evidence from a prospective observational study of Scottish men. Social Science & Medicine, 61(9), 1916-1929]. They suggest that the failure of these variables is indicative of the relative insignificance of psychosocial influences on health. This commentary argues for a different approach to examining these pathways. Efforts to demonstrate the failure of variables to predict health have the usual difficulties of trying to prove the null hypothesis. In this instance, problems in the conceptualization and measurement of psychosocial variables may account for the null results. Psychosocial and material factors are not mutually exclusive but, rather, are complementary. Unexplained variation in health when material factors are accounted for may be explained in part by psychosocial factors and vice versa. Collaboration between researchers who understand each of these domains will yield the greatest benefit in terms of understanding the processes leading to health disparities and providing multiple approaches for eliminating them.