The relativity of relative risks: disadvantage or opportunity?

Psychiatric epidemiologists use many tools, such as relative risks and the related odds such as relative risks and the related odds ratios, that were developed to study chronic ratios, that were developed to study chronic somatic disease. Cancer epidemiologists somatic disease. Cancer epidemiologists identify as a major advantage of relative identify as a major advantage of relative risks that, when appropriately adjusted for risks that, when appropriately adjusted for confounding and effect modification and confounding and effect modification and the individual level, the individual level, they provide stable measures of association in a they provide stable measures of association in a wide variety of populations. When there are wide variety of populations. When there are differences in the effect of exposure for different differences in the effect of exposure for different populations, it is often true that exposure levels populations, it is often true that exposure levels are not the same, or that there are biological are not the same, or that there are biological reasons for the discrepancies in response to the reasons for the discrepancies in response to the same exposure (Breslow & Day,1980). same exposure (Breslow & Day,1980). This may apply in cancer epidemiology, but This may apply in cancer epidemiology, but the special nature of the risk factors and the special nature of the risk factors and outcomes studied by psychiatrists (and also outcomes studied by psychiatrists (and also by those concerned with infectious disease) by those concerned with infectious disease) suggests a more substantial role for the suggests a more substantial role for the sociocultural, environmental and epidemio-sociocultural, environmental and epidemiological contexts in which individuals fall ill. logical contexts in which individuals fall ill. In psychiatric epidemiology relative risks In psychiatric epidemiology relative risks are often conditional, depending first on are often conditional, depending first on the 'overall community's mental health' the 'overall community's mental health' (Rose, 1989) and second on individuals' (Rose, 1989) and second on individuals' 'competing' risks. This limits their applic-'competing' risks. This limits their applicability outside the original study groups. ability outside the original study groups. However, increased attention by psychi-However, increased attention by psychiatric epidemiologists to the origins of this atric epidemiologists to the origins of this variability may give new impetus to social variability may give new impetus to social psychiatric research and practice, and psychiatric research and practice, and stimulate interdisciplinary liaison. stimulate interdisciplinary liaison. The relative risk …