Adaptive changes in chemical activity in certain regions of the brain of former methamphetamine users who have not used the drug for a year or more suggest some recovery of neuronal structure and function, according to an article in the April issue of Archives of General Psychiatry.
Methamphetamine use has been shown to cause abnormalities in brain regions associated with selective attention and regions associated with memory, according to background information in the article. Recent animal and human studies suggest that neuronal changes associated with long-term methamphetamine use may not be permanent but may partially recover with prolonged abstinence.
Thomas E. Nordahl, M.D., Ph.D., of the University of California, Davis, and colleagues compared eight methamphetamine users who had not used methamphetamine for one to five years and 16 recently abstinent methamphetamine users who had not used the drug for one to six months with 13 healthy, non-substance-using controls using a method of brain imaging, proton magnetic resonance spectroscopy (MRS), that allows the visualization of biochemical markers that are linked with damage and recovery to the neurons in the brain.
The researchers measured biomarkers in the anterior cingulum cortex, a region of the brain associated with selective attention. Levels of N-acetylaspartate (NAA), which is present only in neurons, were measured as a marker of the amount of damage (neuronal loss). Choline (Cho), which is generated by the creation of new membranes and, the authors write, "may be an ideal marker to track changes consistent with neuronal recovery associated with drug abstinence," was measured as a biomarker of recovery.
Levels of NAA were abnormally low in all the methamphetamine users, the authors found. Levels were lower relative to the length of methamphetamine use, but did not change relative to the amount of time that the methamphetamine users had been abstinent. The researchers found elevated Cho levels in the methamphetamine users who had not used the drug in one to six months, but normalized levels in the longer abstainers. "In the early periods following methamphetamine exposure, the brain may undergo several processes leading to increased membrane turnover. The relative Cho normalization across periods of abstinence suggests that when drug exposure is terminated, adaptive changes occur, which may contribute to some degree of normalization of neuronal structure and function," they write.
"The understanding of how the human brain can recover or partially recover as a function of extended drug abstinence has important implications both for the neurobiology of addiction and substance abuse treatment," the authors conclude. "Additional longitudinal studies.are needed to further understand the underlying physiological changes of stimulant drugs on the human brain."