Elsevier

Intelligence

Volume 58, September–October 2016, Pages 69-79
Intelligence

Intelligence in youth and mental health at age 50

https://doi.org/10.1016/j.intell.2016.06.005Get rights and content
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open access

Highlights

  • Links between IQ in youth and four mental health outcomes at age 50 were examined.

  • Higher IQ was associated with a greater risk of a depression diagnosis (OR 1.11).

  • Adjusting for adult SES amplified the diagnosis of depression coefficient (OR 1.32)

  • Higher IQ was associated with a lower risk of the other three mental health outcomes.

Abstract

Background

Few cognitive epidemiology studies on mental health have focused on the links between pre-morbid intelligence and self-reports of common mental disorders, such as depression, sleep difficulties, and mental health status. The current study examines these associations in 50-year-old adults.

Methods

The study uses data from the 5793 participants in the National Longitudinal Survey of Youth 1979 cohort (NLSY-79) who responded to questions on mental health at age 50 and had IQ measured with the Armed Forces Qualification Test (AFQT) when they were aged between 15 and 23 years in 1980. Mental health outcomes were: life-time diagnosis of depression; the mental component score of the 12-item short-form Health Survey (SF-12); the 7-item Center for Epidemiological Studies Depression Scale (CES-D); and a summary measure of sleep difficulty.

Results & conclusion

Higher intelligence in youth is associated with a reduced risk of self-reported mental health problems at age 50, with age-at-first-interview and sex adjusted Bs as follows: CES-depression (B =  0.16, C.I. − 0.19 to − 0.12, p < 0.001), sleep difficulties (B =  0.11, C.I. − 0.13 to − 0.08, p < 0.001), and SF-12 mental health status (OR = 0.78, C.I. 0.72 to 0.85, p < 0.001; r =  0.03 p = 0.075). Conversely, intelligence in youth is linked with an increased risk of receiving a diagnosis of depression by the age of 50 (OR 1.11, C.I. 1.01 to 1.22, p = 0.024; r = 0.03, p = 0.109). No sex differences were observed in the associations. Adjusting for adult SES accounted for most of the association between IQ and the mental health outcomes, except for having reported a diagnosis of depression, in which case adjusting for adult SES led to an increase in the size of the positive association (OR = 1.32, C.I. 1.16 to 1.51, p < 0.001).

Keywords

Cognitive epidemiology
Intelligence
Sleep difficulties
Mental health
Depression
SES
Age 50
AFQT
NLSY-79

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