Childhood IQ and Adult Mental Disorders: A Test of the Cognitive Reserve Hypothesis

• Published in: The American journal of psychiatry Vol. 166; no. 1; pp. 50 - 57
• Main Authors: Koenen, Karestan C., Moffitt, Terrie E., Roberts, Andrea L., Martin, Laurie T., Kubzansky, Laura, Harrington, HonaLee, Poulton, Richie, Caspi, Avshalom
• Format: Journal Article
• Language: English
• Published: Arlington, VA American Psychiatric Association 01.01.2009
• Subjects: Adult; Adult and adolescent clinical studies; Alcoholism - diagnosis; Alcoholism - epidemiology; Alcoholism - psychology; Anxiety Disorders - diagnosis; Anxiety Disorders - epidemiology; Anxiety Disorders - psychology; Biological and medical sciences; Bipolar disorder; Bipolar Disorder - diagnosis; Bipolar Disorder - epidemiology; Bipolar Disorder - psychology; Child; Cognition Disorders - diagnosis; Cognition Disorders - epidemiology; Cognition Disorders - psychology; Cognitive ability; Cohort Studies; Cross-Sectional Studies; Depressive Disorder - diagnosis; Depressive Disorder - epidemiology; Depressive Disorder - psychology; Female; Health education; Humans; Intelligence; Longitudinal Studies; Male; Medical sciences; Mental depression; Mental disorders; Mental Disorders - diagnosis; Mental Disorders - epidemiology; Mental Disorders - psychology; Mental health care; Miscellaneous; New Zealand; Odds Ratio; Older people; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Risk; Risk factors; Schizophrenia; Schizophrenia - diagnosis; Schizophrenia - epidemiology; Studies; Substance-Related Disorders - diagnosis; Substance-Related Disorders - epidemiology; Substance-Related Disorders - psychology; Working conditions; New Zealand; Oceania; Human; Social environment; Cognitive reserve; Mental health; Cognition; Concomitant disease; School age; Premorbid intelligence; Follow up study; Adolescent; Young adult; Mental disorder; Birth cohort; Intellectual ability; Severity score; Diagnosis; Predictive factor; Child; Public health; Intelligence quotient
• ISSN: 0002-953X; 1535-7228
• DOI: 10.1176/appi.ajp.2008.08030343

Objective: Cognitive reserve has been proposed as important in the etiology of neuropsychiatric disorders. However, tests of the association between premorbid IQ and adult mental disorders other than schizophrenia have been limited and inconclusive. The authors tested the hypothesis that low childhood IQ is associated with increased risk and severity of adult mental disorders. Method: Participants were members of a representative 1972-1973 birth cohort of 1,037 males and females in Dunedin, New Zealand, who were followed up to age 32 with 96% retention. WISC-R IQ was assessed at ages 7, 9, and 11. Research diagnoses of DSM mental disorders were made at ages 18, 21, 26, and 32. Results: Lower childhood IQ was associated with increased risk of developing schizophrenia spectrum disorder, adult depression, and adult anxiety. Lower childhood IQ was also associated with greater comorbidity and with persistence of depression; the association with persistence of generalized anxiety disorder was nearly significant. Higher childhood IQ predicted increased risk of adult mania. Conclusions: Lower cognitive reserve, as reflected by childhood IQ, is an antecedent of several common psychiatric disorders and also predicts persistence and comorbidity. Thus, many patients who seek mental health treatment may have lower cognitive ability; this should be considered in prevention and treatment planning.