A few decades ago, a widely broadcast television commercial warned about the hazards of drug abuse by portraying an egg sizzling in a hot skillet. “This is your brain on drugs,” a voice portentously warned. In June scientists released actual images of damage inflicted on the brain from habitual use of the highly addictive methamphetamine, or speed. The pictures, published in The Journal of Neuroscience, were as dramatic as the TV spot. Using high-resolution magnetic resonance imaging to map the brains of methamphetamine addicts for the first time, Paul Thompson, at the University of California at Los Angeles School of Medicine, found repeated abuse produced a “forest fire of brain damage.”
The greatest damage was to the limbic system, which controls emotions, moods, rewards, and cravings. Among the 22 addicts whose brains Thompson studied, an average 11.3 percent of limbic cells were destroyed. Both the hippocampus and the cingulate gyrus, two areas of the limbic system associated with memory, showed injury. On average, 7.8 percent of the tissue in the hippocampus, a spoon-size area underneath the frontal lobes, was destroyed. “That’s why they can’t remember a string of words,” Thompson says. “It’s amazing how selective the damage is,” he says. “HIV infections, for example, damage the whole brain, but methamphetamine only attacks these two areas.”
Overall, the parts of the brain harmed by methamphetamine abuse are the same ones affected by the early stages of Alzheimer’s disease, he says. And abuse of the drug is at epidemic proportions: More than 35 million people throughout the world are thought to use it regularly, which is more than twice as many as abuse cocaine (15 million) or heroin (10 million). Surprisingly, methamphetamine addicts’ brains were about 10 percent larger than normal brains, apparently due to inflammation of the brain’s white matter—the nerve cells that link the different thinking centers of the organ. “That’s the opposite of what you would expect. We never found anything like this before,” says Thompson. The good news is that the inflammation is probably reversible if the addict kicks his meth habit.
