"The results indicate that early nicotine exposure can leave a lasting imprint on the brain," said Edward Levin, Ph.D., professor in the psychiatry and behavioral sciences department at Duke University Medical Center and a researcher at Duke's Nicotine Research Center. The study was supported by grants from the National Institute on Drug Abuse and the National Institute of Mental Health.
Most tobacco use begins during adolescence, Levin pointed out. Among smokers in the United States, 88 percent smoked their first cigarette before the age of 18 and 60 percent before age 14. Adolescence is also a crucial period for the brain, he said, in which the final phase of neuron development occurs.
If humans minds react similarly to those of rats the effect of the early exposure is quite deleterious:
To clarify the basis of early nicotine addiction, Levin and colleagues tested for a link between the age of initial nicotine use and addiction in female rats in the laboratory. The researchers provided some rats with nicotine at 40 to 46 days of age, while others were provided nicotine only after 70 to 76 days, once they had reached adulthood. Rats could self-administer a dose of nicotine by pressing a lever.
The adolescent rats self-administered significantly more nicotine than did adults, the researchers found. In a test for chronic nicotine use in the rats during a period of four weeks, animals that began using nicotine during adolescence continued to use more of the drug even after they became adults.
The results suggest that people who begin using nicotine during adolescence may be at greater risk for long-lasting addiction, the team reports.
"The brain continues to develop throughout the teenage years," Levin said. "Early nicotine use may cause the wiring of the brain to proceed inappropriately. In essence, the brains of adolescents who use tobacco may be sculpted around an addiction to nicotine."
This is not an entirely surprising result and, in my view, will eventually be confirmed in humans. The minds of adolescents are undergoing a lot of changes. This suggests a higher degree of plasticity that probably means younger growing minds will change more in response to exposure to drugs. Allowing adolescents easy access to drugs will result in changes to their minds that will last for many years and perhaps for their lifetimes.
Update: The rats used for this experiment were the age equivalent of 14 year old girls.
Update II: Drugs vary in their addictiveness.
According to the Institute of Medicine of the National Academy of Science, 32 percent of people who try tobacco become dependent, as do 23 percent of those who try heroin, 17 percent who try cocaine, 15 percent who try alcohol and 9 percent who try marijuana.
Dr. Cami and Dr. Farré observed that personality traits like risk-taking and novelty-seeking tendencies, as well as mental disorders, are "major conditioning factors in drug addiction."
It would be interesting to see how those figures break out by age, race, and sex. If the results of exposing rats to nicotine at different ages are a measure of a general phenomenon them we'd expect to see higher rates for those who try a gven drug in adolescence as compared to trying it at a later age.
Update III: Technological advances are reducing the need to smuggle drugs as synthetic drug manufacture can be done close to the point of consumption and synthetic drug abuse has now surpassed cocaine and heroin drug abuse.
Ecstasy abuse spiralled 70 percent and amphetamines, such as speed, by 40 percent between 1995 and 2001. By contrast, cocaine and heroin abuse worldwide grew less than one percent each.
Addictive drugs that alter and damage the mind are going to become easier to make and their use is likely to grow.
|Share |||Randall Parker, 2003 September 29 03:26 PM Brain Addiction|