28 March 2000

Speed Kills Brain Cells After Abuse Stops

by Kate Melville

Methamphetamine, also known as speed, crank, crystal or ice, causes brain cell damage evident long after drug abuse has stopped, according to a study published in the March 28 issue of Neurology, the American Academy of Neurology's scientific journal.

"Methamphetamine may be substantially toxic to human brain cells," said study author Thomas Ernst, PhD, of the Harbor-UCLA Research and Education Institute in Torrance, California. "Because methamphetamine may alter brain chemistry in the long term, methamphetamine dependence, as well as dependence on other drugs, should be considered an organic brain disease, and be treated correspondingly."

Researchers used a non-invasive technique to assess certain metabolite or chemical levels in the brain. Previous studies have found that abnormalities in these chemicals are very sensitive indicators for injury to brain cells. The test results for 26 previous methamphetamine abusers were compared to 24 healthy people without a history of drug abuse. The drug abusers had not used methamphetamine for at least two weeks and up to 21 months.

In the methamphetamine abusers, concentrations of the chemical N-acetyl-aspartate were reduced by five percent in the basal ganglia brain region and by six percent in the brain's frontal white matter. N-acetyl-aspartate is a brain metabolite present only in neurons, the brain cells used for thinking.

"Many brain diseases associated with brain cell or neuronal damage or loss, such as Alzheimer's disease and other dementias, epilepsy, multiple sclerosis, brain tumors, stroke and HIV brain diseases, consistently have shown decreased N-acetyl-aspartate," said Ernst. "Therefore, the reduced concentration of N-acetyl-aspartate in the drug users' brains suggests neuronal loss or damage as a result of long-term methamphetamine use." Methamphetamine causes a massive release of the chemical dopamine within the brain. The basal ganglia brain region has a high density of dopaminergic neurons, which may be why it is more affected by methamphetamine toxicity. Previous studies have shown that methamphetamine is neurotoxic in animals and causes profound long-term abnormalities in the dopaminergic system in humans.

Ernst said, "Subjects who had used the largest amounts (in grams) of methamphetamine during their drug careers showed the lowest concentrations of N-acetyl-aspartate in the frontal white matter. This suggests that higher doses of methamphetamine cause more damage to the neurons in this brain region."

The study also found an eight percent reduction in creatine in the basal ganglia, along with a 13 percent increase in choline-containing compounds and an 11 percent increase in myo-inositol in the frontal gray matter of the drug users. Creatine reflects two chemicals involved in cell energy metabolism.

"Myo-inositol is a metabolite present in a type of brain cell called glial cell," explained Ernst. "Choline compounds, present in cell membranes, are substantially higher in glial cells than in neuronal cells. Therefore, the increased myo-inositol and choline concentrations most likely represent an increased number or size of glial cells, as a reaction to the injurious effects of methamphetamine."

The study assessed potential long-term damage to the human brain due methamphetamine use, but not whether these changes are permanent. However, some animal research has shown brain abnormalities for up to four years after exposure to methamphetamine. Ernst and other researchers are performing more extensive studies to determine whether the brain changes may be reversed with treatment.

Methamphetamine abuse has risen in recent years with some hospitals reporting a six-fold increase in methamphetamine-related emergency department cases over the past decade, said Ernst. A 1996 survey reported that nearly five million Americans have used methamphetamine at some time in their lives, up from about 3.8 million Americans in 1994. Methamphetamine abuse is not simply an urban problem according to Ernst. Recent reports show that methamphetamine use among rural-American high school students is up to 100 percent higher compared to students living in metropolitan areas.