New research published in the August 2005 issue of the American Journal of Psychiatry indicates that methamphetamine abuse and HIV infection cause significant alterations in the size of certain brain structures, which may be associated with impaired cognitive functions. Co-occurring methamphetamine abuse and HIV infection appears to result in greater impairment than each condition alone.
"Methamphetamine abuse is linked with HIV, hepatitis C, and other sexually transmitted diseases, not only by the use of contaminated injection equipment, but also due to increased risky sexual behaviors," says Dr. Nora D. Volkow, director of the National Institute on Drug Abuse (NIDA), National Institutes of Health, which helped support the research. "These findings show that methamphetamine abuse and HIV infection each cause significant changes in the volume of brain gray matter structures and cognitive function."
Scientists led by Dr. Terry Jernigan of the HIV Neurobehavioral Research Center of the University of California-San Diego conducted brain scans to analyze structural volume changes in 103 adults divided among four populations: methamphetamine abusers who were HIV-positive; methamphetamine abusers who were HIV-negative; nonabusers who were HIV-positive; and nonabusers who were HIV-negative.
They also assessed the ability to think and reason using a detailed battery of tests that examined speed of information processing, attention/working memory, learning and delayed recall, abstraction/executive functioning, verbal fluency, and motor functioning.
Thought, Reasoning, MemoryThey observed that methamphetamine abuse is associated with increases in the volume of the brain's parietal cortex (which helps people to understand and pay attention to what's going on around them) and basal ganglia (linked to motor function and motivation).
HIV infection is associated with prominent volume losses in the cerebral cortex (involved in higher thought, reasoning, and memory), basal ganglia, and hippocampus (involved in memory and learning).
The scientists stress that among the recent methamphetamine abusers in the study, the degree of volume increase in the parietal cortex was associated with worse cognitive function.
Impaired Decision Making"In HIV-infected people, the cognitive impairments are associated with decreased employment and vocational abilities, difficulties with medication management, impaired driving performance, and problems with general activities of daily living, such as managing money," says Dr. Jernigan. "The impact of methamphetamine on daily functioning is less well studied, although it is known that abusers of the drug have impaired decision-making abilities. These could potentially affect treatment and relapse prevention efforts, as well as things like money management and driving performance."
The brain volume changes associated with methamphetamine abuse did not correlate with the amount of the drug a person ingested. However, the study results suggest that younger methamphetamine abusers showed larger effects in some brain regions. Among HIV-infected individuals, the researchers noted a direct association between the severity of the infection and greater loss of brain matter.
In methamphetamine abusers who are also HIV-positive, decreased volumes are correlated with increased cognitive impairment in one brain region, the hippocampus.
Brain InflammationDr. Jernigan explains that the changes seen in brain structures could be the result of inflammation in the brain and/or compensatory changes associated with methamphetamine toxicity. Also, brain inflammation associated with HIV infection may contribute to brain cell shrinkage or loss.
Dr. Volkow says medications that reduce inflammation might be useful in treating methamphetamine abusers.
"The effects of methamphetamine and HIV on the brain are distinct but may affect the same brain regions, so understanding how the underlying mechanisms interact also may lead to more effective therapies and the information should be useful in guiding future studies," Dr. Volkow concludes.