| Marijuana May Stem Alcohol's Shrinkage of Teens' Brains |
|
|
|
| Written by Brenda Shoop | |
| Thursday, 27 March 2008 | |
Marijuana May Stem Alcohol's Shrinkage of Teens' Brains MONTREAL -- Teenagers who report heavy alcohol use have reduced hippocampal volume, compared with their nondrinking peers, but those who combine marijuana with heavy drinking do not show these abnormalities, Susan Tapert, Ph.D., reported at the annual conference of the EEG and Clinical Neuroscience Society.  "It's possible there could be some neuroprotective effect of marijuana against the effects of alcohol," said Dr. Tapert of the University of California, San Diego, noting that simultaneous marijuana and alcohol use has been shown to reduce blood alcohol levels. However, another potential explanation is that "there may be competing pathologies that cancel each other out," she said in an interview.
In the study, which she presented at the meeting, her group used magnetic resonance imaging to compare hippocampal volumes in 16 adolescent alcohol users, 26 marijuana and alcohol users, and 21 abstainers. The subjects were aged 15-18 years, and MRI was performed after at least 2 days of abstinence from all substances. The smaller hippocampal volume seen in the alcohol users resulted in an abnormal pattern of right-to-left hippocampal asymmetry, compared with both controls and users of marijuana plus alcohol--and this abnormal asymmetry was related to memory function.
She went on to speculate that the pathological lack of correspondence between performance and volumes might be attributable to a combination of simultaneous microstructural factors, such as edema, atrophy, altered myelination, and altered synaptic pruning. Brain volume studies may show little effect of marijuana use, but brain function tests tell another story, Dr. Tapert said. In another recent study by her group, although marijuana-using adolescents who had abstained for 28 days performed similarly to nonusers on an inhibition task, functional MRI showed evidence of more brain processing effort to achieve adequate performance levels in the users (Psychopharmacology [Berl] 2007;194:173-83). And in another study by her group, 31 marijuana-using adolescents were compared with 34 controls on neuropsychological functioning. Users had slower psychomotor speed and poorer complex attention, verbal learning and memory, and planning and sequencing ability, even after more than 23 days of abstinence (J. Int. Neuropsychol. Soc. 2007;13:807-20). Dr. Tapert suggested that some brain function abnormalities noted in adolescent marijuana users may not be caused by substance use but could possibly predate it. Marijuana may be neuroprotective, or there may be competing pathologies that cancel each other out. (c)Valérie Mariotte/FOTOLIA Original Article Here>> PII: S1097-8690(08)70332-9 doi:10.1016/S1097-8690(08)70332-9 (c) 2008 Elsevier Inc. All rights reserved. |
|
| Last Updated ( Thursday, 27 March 2008 ) |
| < Prev | Next > |
|---|
