Cognitive Ability in Early Adulthood and Risk of 5 Specific Psychiatric Disorders in Middle Age: The Vietnam Experience Study | Psychiatry | JAMA Psychiatry | JAMA Network
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Original Article
December 1, 2008

Cognitive Ability in Early Adulthood and Risk of 5 Specific Psychiatric Disorders in Middle Age: The Vietnam Experience Study

Author Affiliations

Author Affiliations: Medical Research Council Epidemiology Resource Centre, University of Southampton, Southampton, England (Dr Gale); Centre for Cognitive Ageing and Cognitive Epidemiology, Department of Psychology, University of Edinburgh, Edinburgh, Scotland (Drs Deary and Batty); Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, North Carolina (Drs Boyle and Barefoot); Institute of Public Health, University of Southern Denmark, Copenhagen (Mr Mortensen); and Medical Research Council Social and Public Health Sciences Unit, University of Glasgow, Glasgow, Scotland (Dr Batty).

Arch Gen Psychiatry. 2008;65(12):1410-1418. doi:10.1001/archpsyc.65.12.1410

Context  Lower cognitive ability is a risk factor for some forms of psychopathology, but much of the evidence for risk is based on individuals who required specialist care. It is unclear whether lower ability influences the risk of particular patterns of comorbidity.

Objective  To examine the relation between premorbid cognitive ability in early adulthood and the risk of major depression, generalized anxiety disorder (GAD), posttraumatic stress disorder (PTSD), alcohol and other drug abuse or dependence, and comorbid forms of these conditions in midlife.

Design  Prospective cohort study in which cognitive ability was measured on enlistment into military service at a mean age of 20.4 years and psychiatric disorder was assessed by structured diagnostic interview at a mean age of 38.3 years.

Setting  The United States.

Participants  A total of 3258 male veterans, participants in the Vietnam Experience Study.

Main Outcome Measures  Major depression, GAD, PTSD, and alcohol or other drug abuse or dependence since enlistment and currently, diagnosed according to the DSM-III.

Results  Lower cognitive ability was associated with an increased risk of depression, GAD, alcohol abuse or dependence, and PTSD and with some patterns of comorbidity. For a 1-SD decrease in cognitive ability, unadjusted odds ratios (95% confidence interval) for having these disorders currently were 1.32 (1.12-1.56) for depression, 1.43 (1.27-1.64) for GAD, 1.20 (1.08-1.35) for alcohol abuse or dependence, 1.39 (1.18-1.67) for PTSD, 2.50 (1.41-4.55) for PTSD plus GAD, 2.17 (1.47-3.22) for PTSD plus GAD plus depression, and 2.77 (1.12-6.66) for all 4 disorders. Most associations remained statistically significant after adjustment for confounders.

Conclusions  Lower cognitive ability is a risk factor for several specific psychiatric disorders, including some forms of comorbidity. Understanding the mechanisms whereby ability is linked to individual patterns of psychopathology may inform intervention.