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Original Article
March 2003

A Twin Study of the Neuropsychological Consequences of Stimulant Abuse

Author Affiliations

From the Department of Psychiatry, Massachusetts Mental Health Center, Harvard Medical School (Drs Toomey, Lyons, Seidman, Faraone, and Tsuang), the Harvard Institute of Psychiatric Epidemiology and Genetics (Drs Toomey, Lyons, Seidman, Faraone, and Tsuang), the Department of Psychology, Boston University (Drs Toomey and Lyons), and the Department of Epidemiology, Harvard School of Public Health (Dr Tsuang), Boston, Mass; the Brockton/West Roxbury Veterans Affairs Medical Center, Brockton, Mass (Drs Toomey, Lyons, Seidman, Faraone, and Tsuang); and the Department of Medicine, Washington University (Drs Eisen, Xian, and Chantarujikapong), the Research and Medical Service, St Louis Veterans Affairs Medical Center (Drs Eisen, Xian and Chantarujikapong), and the School of Public Health, St Louis University (Dr Chantarujikapong), St Louis, Mo. Dr Toomey is now also with the Department of Psychiatry, Massachusetts General Hospital, Charlestown.

Arch Gen Psychiatry. 2003;60(3):303-310. doi:10.1001/archpsyc.60.3.303
Abstract

Background  Previous studies document neuropsychological deficits associated with stimulant abuse, but findings are inconsistent.

Methods  We identified 50 twin pairs in which only 1 member had heavy stimulant abuse (cocaine and/or amphetamines) ending at least 1 year before the evaluation. The co-twin control research design controls for familial vulnerability and makes it easier to identify neuropsychological deficits that are consequences of stimulant abuse. Subjects were administered an extensive neuropsychological test battery organized into the following 5 functions: attention, executive functioning, motor skills, intelligence, and memory.

Results  Multivariate tests showed that abusers performed significantly worse than nonabusers on functions of attention and motor skills. Within each of these functions, univariate tests showed that abusers performed significantly worse on certain tests of motor skills and attention. In contrast, abusers performed significantly better on one test of attention measuring visual vigilance. Within the abuser group, higher levels of stimulant use were largely uncorrelated with neuropsychological test scores, although a few significant correlations indicated better functioning with more stimulant use.

Conclusions  With ideal controls, this study demonstrates that deficits in attention and motor skills persist after 1 year of abstinence from stimulant use and raises hypotheses regarding relative strengths on a vigilance task among abusers.

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