The Lothian birth-cohort studies are two ongoing cohort studies which primarily involve research into how childhood intelligence relates to intelligence and health in old age. The Lothian Birth Cohort studies of 1921 and 1936 have, respectively, followed up Lothian-based participants in the Scottish Mental Surveys of 1932 and 1947 in old age. Scottish Mental Survey data has provided a measure of the intelligence of Lothian Birth Cohort participants at age 11, which has enabled the investigation of how childhood intelligence relates to cognition, mental health and physical health in old age.