|PET scan images of the brains of a methamphetamine user and of a control subject.|
It goes by many names, but whether its called "speed," "ice," "chalk," "crystal" or "glass," methamphetamine is a highly addictive stimulant. And while the problems associated with drug abuse are familiar to most people, new research has added to the list.
Scientists are now able to look directly at the brain of drug users and have found that methamphetamine damages the brain, and its effects continue long after people stop using it.
Looking at the brain
In the March issue of The American Journal of Psychiatry. scientists at Brookhaven National Laboratory report the results of two studies which show that methamphetamine causes changes in two systems of the brain. People who abuse it have reduced cognitive and motor functions, even almost a year after they quit. "These types of changes weve never observed with other drugs, and weve studied cocaine, heroin, marijuana and alcohol," says Nora Volkow, a psychiatrist at Brookhaven who led the studies.
Methamphetamine acts on the brain by prolonging its pleasure signal. Dopamine, a neurotransmitter that causes us to feel pleasure, is normally transported back into the nerve cells that produce it by a protein called dopamine transporter. Volkow and her team injected volunteers with a radioactive substance that finds and sticks to the protein. They then scanned their brains with a special device called a positron emission tomography (PET) camera. The PET camera picks up the signal of the radioactive tracer, showing where its bound to the dopamine transporters. The lower the signal, the lower the number of transporters.
The study involved 15 detoxified methamphetamine addicts (who hadnt used it for at least two weeks) and 18 healthy people who had never used the drug. Addicts showed a reduction in dopamine transporters, even more than 11 months after subjects had stopped using methamphetamine. Neuropsychological tests showed for the first time that this reduction translates into memory impairment and slowed motor function.
"The changes were observing are equivalent to 40 years in loss of transporter," says Volkow, meaning that in terms of dopamine transporters, its as if the subjects had aged 40 years. In three of the speed abusers, the levels of dopamine transporters fell to levels seen in patients with mild Parkinsons disease. Its possible that the combination of aging and drug abuse will eventually put addicts at risk for some of the same symptoms associated with the disease, according to the study.
A second study looked at brain metabolism to see if methamphetamine effects anything besides dopamine transporters. Researchers found higher brain metabolism in abusers, which Volkow says is indicative of inflammation and a "physical insult" to the brain. She called the findings surprising, since previous drug studies have shown decreased metabolism.
|Man entering a PET scanner.|
In recent years, researchers have come to understand how addiction works. "The reason its so difficult to stop is because alcohol and substance abuse actually change your brain," says National Institute on Drug Abuse (NIDA) director Alan Leshner. But its effects go way beyond that organ. "One of the things weve learned about addiction is that it is a whole person illness. It interferes with all aspects of the addicts life, not just their biology," says Leshner.
According to a survey by the NIDA, about 4.9 million Americans have tried it at some point in their lives. A recent NIDA report found that methamphetamine abuse is rising overall, as well as spreading to new areas of the country.
Experts are trying to figure out what makes certain people follow the path to drug addiction. "Were beginning to understand that differences in people, biological differences, genetic makeup, contribute to their behavior," says Leshner. "A little taste of the drug, stress, and other such things push them to do it."
Leshner says that addicts cant stop taking drugs without serious medical treatment that relieves the brain damage it causes. "Addiction is actually a brain disease drug addicts have," says Leshner. "Like other patients, they need treatment."