The detrimental effects of heavy cocaine use on an individual's manual dexterity, problem solving, and other critical skills can last for up to a month after the drug was taken, according to a study reported in the Summer issue of The Journal of Neuropsychiatry and Clinical Neurosciences. The study, which was conducted by researchers at the Intramural Research Program of the National Institute on Drug Abuse(NIDA) and Johns Hopkins University School of Medicine, found that heavy cocaine users were outperformed by moderate users and non-users on most tests measuring verbal memory, manual dexterity, and other cognitive skills. Heavy cocaine use was defined as two or more grams a week.
NIDA Director Dr. Alan I. Leshner says, "This study adds to the accumulating - and worrisome - evidence that heavy use of cocaine can result in persistent deficits in the skills needed to succeed in school and on the job. Cocaine users are risking their futures. For them, prevention and effective treatment become critical public health priorities."
"These findings underscore the connection between cocaine use and neurobehavioral effects," says Dr. Karen I. Bolla, Associate Professor of Neurology at Johns Hopkins. "While the intensity (grams per week) of cocaine use was more closely associated with decreased performance than the duration of use, all cocaine users in the study experienced reduced cognitive function."
This is the second recent study in which Dr. Bolla has identified persistent cognitive problems in former heavy drug users. In the December 1998 issue of Neurology, she published results showing memory impairment associated with the heavy use of the drug Ecstasy, also known as MDMA. In that study, too, the problem was related to the amount of the drug taken and lasted at least two weeks after stopping use.
Dr. Bolla and Jean Lud Cadet, M.D., Clinical Director and Chief of Neuropsychiatry at the NIDA Intramural Research Program, studied 30 individuals who had used cocaine at least four times a month for one year or longer and gave a urine sample positive for cocaine at the time of admission into the study.
This group was compared to a control group of 21 individuals with no history of drug use except perhaps nicotine, who said they had not had more than 4 drinks of alcohol in the past 30 days. Cocaine users and controls were similar with respect to age, education, and intelligence. None had any current or past history of psychiatric disorder.
The cocaine users were interviewed about how long they had been using cocaine, how many times per week they used it, and their weekly intake in grams. They were admitted to the NIDA Clinical Inpatient Research Unit, where they remained drug free for 30 days.
The cocaine users were given a battery of neuropsychological tests on the 28th or 29th day after admission to the research unit. Those who reported the heaviest use, as measured by grams per week, performed much worse in most aspects of the testing than did light or moderate cocaine users and non-users.
Dose-related effects were seen primarily on tasks involving the prefrontal cortex, which is the area of the brain most responsible for attention/concentration, planning, and reasoning. The heaviest cocaine users showed slower median reaction times and poorer attention and concentration.
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