Heavy use of cocaine impairs memory, manual dexterity and decision-making for at least a month after the drug was last taken, according to a new study of Baltimore drug users by researchers at the National Institute on Drug Abuse.
The study, led by neurologist Karen I. Bolla of the Johns Hopkins University, adds to the evidence that the powerful high experienced by cocaine users is accompanied by long-lasting harm to brain functioning.
The researchers said their work suggests that the brain damage caused by cocaine might set up a devastating spiral by making it harder for the drug user to quit. That's because the damage caused by cocaine occurs in the brain's prefrontal cortex, which is responsible for monitoring behavior and inhibiting bad behavior.
Traditionally, drug addiction was attributed to moral flaws or "weak character," she said. "Now we know this drug actually changes the brain. It may well make it more difficult to stop."
The new paper, published in the Journal of Neuropsychiatry and Clinical Neuroscience, is written by Bolla, Dr. Jean Lud Cadet and Dr. Richard Rothman, both of NIDA. They recruited their 30 subjects, mostly smokers of crack, between 1993 and 1995 at the federal institute's clinical research unit, located on the Hopkins Bayview campus in East Baltimore.
Cadet said one of the biggest challenges was finding chronic cocaine users who did not have a history of abusing other drugs -- and who were willing to give up cocaine for a month. The cocaine users had to reside in the NIDA unit for the 30 days before testing to make certain they were drug-free.
Their performance on a battery of tests was compared to that of a control group of 21 people who had no history of drug use but matched the cocaine users in age, education and IQ score.
Dr. Alan I. Leshner, director of NIDA, said the study documents behavioral changes that appear to correspond to changes found in brain scans of cocaine users.
"It's brain biology and behavior coming together," Leshner said. "It's a dramatic demonstration that there are residual effects of cocaine that hurt the skills people need to succeed in school and at work."
While the first research demonstrating a long-term impact of cocaine on memory and other mental functions was published in 1993, the current study is the first to find a direct relationship between the amount of cocaine used and the degree of impairment.
The NIDA study found that people who reported heavy cocaine use -- consumption of two grams or more per week -- consistently performed worse on the neurological tests than those who reported lighter use.
Dr. Tony Strickland, a neuropsychologist at Charles Drew Medical School in Los Angeles and author of the first study showing lasting brain changes from cocaine use, said the new paper is "enormously important" in linking quantity of cocaine used to damage done.
But he cautioned that the work would have to replicated by other scientists. So far, he said, he has not been able to demonstrate a dose-related impact in his own research.
Strickland said drugs damage the brain in ways that are not always so different from that caused by physical blows.
"The brain doesn't necessarily distinguish between whether you were hit in the head by a ball-peen hammer or whether you suffered this chemical insult," he said.
Michael M. Gimbel, director of substance abuse for Baltimore County, said the research coincides with the subjective impressions of those who counsel cocaine abusers.
"It's always reassuring to find technical evidence to confirm what those of us in the field experience with cocaine addicts every day," said Gimbel, who oversees the county's treatment programs, including one in Towson tailored to cocaine users. "It will help us in educating the addicts about the effects of the drug."
Gimbel said he found intriguing the idea that cocaine might injure the part of the brain responsible for impulse control.
"Every coke addict that gets clean says, `Why in the world did I do that to myself?' This helps answer that question," he said.
Pub Date: 8/01/99