Public Release: 

Study of twins reveals changes in attention and motor skills after heavy stimulant abuse

NIH/National Institute on Drug Abuse

In a study supported by the National Institute on Drug Abuse (NIDA), researchers found that heavy stimulant abuse can result in changes in attention and motor skills that can persist for at least a year.

The investigators studied 50 pairs of twins; in each pair, one twin had a history of abusing cocaine and/or methamphetamine and the other had no history of drug abuse. Thirty-one monozygotic (identical) and 19 dizygotic (fraternal) adult male twin pairs were tested for attention and motor skills, executive functioning, intelligence, and memory at least one year after the drug-using twin's last-reported use of stimulants.

The researchers, led by Dr. Rosemary Toomey from Massachusetts General Hospital, found that the twin with a history of stimulant abuse performed significantly worse on several tests of attention and motor skills than did the sibling who had never used drugs.

However, abusers outperformed their non-drug-using twin on visual vigilance, a test measuring the ability to pay attention over time.

WHAT IT MEANS: This study provides evidence that stimulant abuse can result in long-term residual neuropsychological effects.

The study was published in the March 2003 issue of the journal Archives of General Psychiatry.


The National Institute on Drug Abuse (NIDA) is a component of the National Institutes of Health, U.S. Department of Health and Human Services. NIDA supports more than 85 percent of the world's research on the health aspects of drug abuse and addiction. The Institute carries out a large variety of programs to ensure the rapid dissemination of research information and its implementation in policy and practice. Fact sheets on the health effects of drugs of abuse and other topics are available in English and Spanish. These fact sheets and further information on NIDA research and other activities can be found on the NIDA home page at

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