Intelligence: Is It the Epidemiologists' Elusive "Fundamental Cause" of Social Class Inequalities in Health?

Abstract

Virtually all indicators of physical health and mental competence favor persons of higher socioeconomic status (SES). Conventional theories in the social sciences assume that the material disadvantages of lower SES are primarily responsible for these inequalities, either directly or by inducing psychosocial harm. These theories cannot explain, however, why the relation between SES and health outcomes (knowledge, behavior, morbidity, and mortality) is not only remarkably general across time, place, disease, and kind of health system but also so finely graded up the entire SES continuum. Epidemiologists have therefore posited, but not yet identified, a more general "fundamental cause" of health inequalities. This article concatenates various bodies of evidence to demonstrate that differences in general intelligence (g) may be that fundamental cause.

Brain volumetric changes and cognitive ageing during the eighth decade of life

“…That is, cognitive tests (of Memory and Speed) were a predictor of less subsequent change in brain volume. It is possible that this is due to the established relations of cognitive ability with health behaviors: for instance, individuals with better cognitive ability tend to smoke less and exercise more (Gottfredson, 2004), and these lifestyle factors may impact brain structure (e.g. [Almeida et al, 2011; Hillman et al, 2008]; note that such factors were not measured in this study).…”

Familial transmission of derived phenotypes for molecular genetic studies of substance use disorders

“…Since the time of Spearman, many researchers have posited that cognition is comprised of a general intelligence (g factor) that serves as a foundation for specific strengths and weaknesses in areas such as memory and attention. Gottfredson (2004) presents evidence that g is a strong predictor of health outcomes, including cigarette, alcohol and substance use, as well as accidents related to use.…”

“…Since the time of Spearman, many researchers have posited that cognition is comprised of a general intelligence (g factor) that serves as a foundation for specific strengths and weaknesses in areas such as memory and attention. Gottfredson (2004) presents evidence that g is a strong predictor of health outcomes, including cigarette, alcohol and substance use, as well as accidents related to use.Although categorical systems such as DSM-IV tend to emphasize differences among disorders, dimensional approaches to psychopathology have suggested that one or more general psychopathology factors may exist (Helzer, et al, 2006). A good example is the Child Behavior Checklist (CBCL), which includes broadband internalizing and externalizing scales as well as narrower clinical scales assessing specific components of psychopathology.…”

Social discounting rate is negatively correlated with fluid intelligence

“…From the perspective of Millet & Dewitte's hypothesis referenced above, particularly important is the relationship between intelligence and access to resources. Studies have demonstrated that as a predictor of socioeconomic status intelligence is more accurate than the status of parents (Gottfredson, 2004). Whether measured in childhood or adulthood, intelligence is predictive for the social status of occupation and income (correlation of 0.51 and 0.31, respectively) (Judge, Higgins, Thoresen & Barrick, 1999).…”