Methamphetamine

Current research suggests neuronal changes associated with long-term
methamphetamine abuse, such as disturbances in memory and selective attention, may not always be permanent. In fact, these neurons may partially recover with prolonged abstinence.

Dr. Thomas Nordahl and colleagues from University of California at Davis Imaging
Research Center used magnetic resonance spectroscopy (MRS) to examine metabolite levels in 2 brain regions responsible for selective attention, the anterior cingulum and the primary visual cortex.

A total of 24 abstinent methamphetamine abusers were matched with 13 controls and divided into 2 groups: distantly abstinent (1 year to 5 years) and recently abstinent (1 month to 6 months). The researchers examined correlations between years of usage, months of abstinence, and metabolites marking cell functions.

Abnormal metabolite levels were found in the brains of both recently and distantly abstinent methamphetamine abusers. Because certain metabolite levels often indicate neuronal health, low N-acetylaspartate (NAA)-to-creatine ratios over an extended period of drug abstinence may suggest long-lasting neuronal injury. Furthermore, the researchers observed that abnormally high choline-to NAA ratios became normal in abstaining methamphetamine abusers following extended periods of remission. This finding suggests an adaptive response by the brain to neuronal changes following periods of abstinence.

What it means: This study provides additional insight on the human brain's ability to at least partially recover from methamphetamine abuse. If altered neuronal tissues are capable of recovery following sustained abstinence, new hope may exist for substance abuse treatment patients. Additional studies are needed to explore the possibility of neurochemical rehabilitation in recovering substance abusers.

This study was published in the April 2005 issue of Archives of General Psychiatry.

NIDA NewsScan, September 7, 2005

Results from a NIDA-funded study indicate that long-term methamphetamine abuse impairs selective inhibition--the ability to filter distracting and conflicting information.

Dr. Ruth Salo and colleagues from University of California, Davis tested 34 long-term, but currently abstinent methamphetamine abusers to determine whether task-shifting and/or selective attention processes were impaired by long-term methamphetamine abuse.

Participants repeated word/number sequences while suppressing conflict and/or switching attention to specific word/number cues. Subjects were also given a series of repeat sequences and switched on every second trial (AABBAABB). Task performance was based on response time and error rate. The researchers observed that methamphetamine abusers committed more errors on trials containing built-in distractions and conflicting information. In contrast, methamphetamine abusers performed similarly to controls on tests requiring them to alternate between differing tasks.

What it means: The ability to pay attention is influenced by several distinct processes. This research suggests that long-term methamphetamine abuse impairs the ability to filter distracting and conflicting information. Because attention is a fundamental building block of many cognitive functions, impairments in selective inhibition should be taken into account when devising drug treatment programs.

The scientists published this study in the February 2005 issue of Biological Psychiatry.

NIDA NewsScan, August 23, 2005

Researchers from the University of California, Los Angeles, have found more evidence that methamphetamine abuse may cause alterations in the brain. The researchers used a highly sensitive technique called quantitative electroencephalography (QEEG) to assess electrical activity in the brain, or “brainwaves,” of recently abstinent methamphetamine abusers and nonusers. Excess amounts of slow brainwaves—delta and theta—have been associated with head injuries and memory problems.

For the study, Dr. Thomas Newton and colleagues recruited methamphetamine users who reported using at least one-half gram of the drug per week for the previous 6 months. After four days of methamphetamine abstinence, the researchers obtained QEEG recordings of the users’ brains. The scientists also obtained QEEG recordings from healthy nonusers. The researchers found that methamphetamine users had increased delta and theta brainwave activity compared to nonusers.

What it means: These findings indicate that methamphetamine abuse may result in functional changes in the brain that are similar to those seen in people with degenerative brain diseases.

This study, funded by NIDA, was published in the March 2003 issue of the journal Clinical Neurophysiology .

NIDA NewsScan, July 30, 2003

Study of Twins Reveals That Changes in Attention and Motor Skills
Persist at Least a Year after Heavy Stimulant Abuse

In a study supported by the National Institute on Drug Abuse (NIDA), researchers found that heavy stimulant abuse can result in changes in attention and motor skills that can persist for at least a year.

The investigators studied 50 pairs of twins; in each pair, one twin had a history of abusing cocaine and/or methamphetamine and the other had no history of drug abuse. Thirty-one monozygotic (identical) and 19 dizygotic (fraternal) adult male twin pairs were tested for attention and motor skills, executive functioning, intelligence, and memory at least one year after the drug-using twin’s last-reported use of stimulants.

The researchers, led by Dr. Rosemary Toomey from Massachusetts General Hospital, found that the twin with a history of stimulant abuse performed significantly worse on several tests of attention and motor skills than did the sibling who had never used drugs. However, abusers outperformed their non-drug-using twin on visual vigilance, a test measuring the ability to pay attention over time.

What it means: This study provides evidence that stimulant abuse can result in long-term residual neuropsychological effects. The study was published in the March 2003 issue of the journal Archives of General Psychiatry .

NIDA NewsScan, April 9, 2003

Methamphetamine, Cocaine Abusers Have Different Patterns of Drug
Use, Suffer Different Cognitive Impairments

Studies supported by NIDA show that methamphetamine abusers typically use the drug 20 days per month, beginning early in the morning and using it at regular intervals throughout the day. In contrast, cocaine abusers are more likely to exhibit a “binge” pattern. They use the drug fewer days per month, typically in the evening rather than in the daytime, and use it continuously over several hours. Both drugs cause deficits in measures of reasoning and concentration, but methamphetamine abusers perform more poorly than cocaine abusers on tests measuring perceptual speed and the ability to manipulate information, according to Dr. Sara Simon of the University of California, Los Angeles.

The typical methamphetamine abuser reported using the drug when he or she first got up in the morning and then using it approximately every two to four hours during the waking day. Most of the descriptions of use more closely resembled taking a medication than using a drug for pleasure. Cocaine abusers, however, reported patterns of use that began in the evening and continued until all the cocaine had been used.

Both drugs are associated with similar cognitive deficits, although some types of impairment differ. The most striking difference is that methamphetamine abusers had more trouble than cocaine abusers with tasks requiring attention, organizing information, and switching points of view.

What it means: These studies add important details to our understanding of the real-world characteristics of methamphetamine and cocaine use. This understanding can be incorporated into the development of treatment strategies that help abusers avoid or cope with situations that put them at risk for relapse and give them behavioral tools they can learn, understand, and apply in those situations. Dr. Simon and her colleagues described their findings in a special methamphetamine issue of Journal of Addictive Diseases (Vol. 21, Number 1, 2002).

NIDA NewsScan, July 31, 2002

Researchers at the University of Chicago, in experiments with mice, have found that prenatal exposure to methamphetamine increases response to the toxic effects of the drug in adult males. Some effects of prenatal methamphetamine exposure were observed in female offspring, but were much less than those seen in the males.

The investigators say these findings may raise concerns for male methamphetamine abusers whose mothers used the drug while pregnant. The neurotoxic risk from using methamphetamine as adults may be greater for men who were exposed prenatally. Methamphetamine toxicity is characterized by persistent decreases in the levels

of dopamine and serotonin in certain brain regions. It is known that in humans, dopamine deficits are associated withsymptoms of Parkinson's disease.

What it means: This finding, coupled with the increasing use of club drugs, such as methamphetamine, by women of childbearing age, makes this issue a potential public health concern.

The researchers, led by Dr. Alfred Heller, published their findings in the August 2001 issue of the Journal of Pharmacology and Experimental Therapeutics .

NIDA NewsScan, October 16, 2001