Objective: Researchers in many fields are interested in the robust observation that higher socioeconomic status (SES) is associated with better mental and physical health. Prominent explanations for the association involve effects of stress due to relative material and social adversity in lower socioeconomic environments, but early-life intelligence may also contribute directly to both later-life socioeconomic status and health. Here, we evaluated the effects of early-life IQ on mental and physical health outcomes at age 70, in the context of effects of SES.
Design: The Lothian Birth Cohort of 1936 took part in the Scottish Mental Survey of 1947, providing a measure of IQ at age 11. They have been extensively surveyed at age 70.
Main outcome measures: Body mass index, constraints on daily life activities, hospital anxiety and depression, number of diseases, level of physical activity, weekly units of alcohol consumption, and pack-years of smoking.
Results and conclusion: SES had apparently direct effects on most outcomes, but age 11 IQ was also involved in several, either directly or because it contributed to SES. Several interactions helped to integrate these associations. High age-11 IQ tended to buffer effects of adverse environments on physical and mental problems in old age.
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