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.
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