Skip to comments.Very Heavy Pot Use Clouds Mental Function: Study
Posted on 11/29/2002 2:18:13 PM PST by Libloather
Very Heavy Pot Use Clouds Mental Function: Study
1 hour, 58 minutes ago
By Dana Frisch
NEW YORK (Reuters Health) - People who smoked unusually large amounts of marijuana performed worse on tests of mental function than their peers who smoked less pot, even after a 30-day abstinence period, according to a new report.
Heavy users performed worse on 69% of the 35 tasks than light users, though their performances were not "clinically abnormal," the researchers found. The 22 participants were admitted to hospital during the course of the study and submitted to random urine tests to ensure they remained abstinent.
Lead author Dr. Karen Bolla characterized the study group as being "unusual" because of the large number of joints they smoked per week. Heavy users smoked on average 91 joints a week, or about 13 a day, while light smokers smoked an average of 11 marijuana cigarettes a week.
Bolla, who is an associate professor of neurology and psychiatry at Johns Hopkins University School of Medicine in Baltimore, Maryland, said the results cannot be generalized to social smokers or those who use pot for medicinal purposes, because they smoke far less marijuana. The potency might also differ, she said.
"What this study shows is that marijuana can be neurotoxic if you smoke a lot of it," Bolla told Reuters Health. She said this is particularly concerning since the average age of study participants was 22 years old, and the brain is still developing at that age. "You're putting a lot of foreign stuff in there that we don't really know what it does to a developing brain," she said.
The study, published in the November issue of the journal Neurology, found that the mental functions most severely impacted were memory, executive function (overall reasoning and functioning) and manual dexterity.
Bolla writes that these tasks in particular were affected because they are controlled by the hippocampus, prefrontal cortex and cerebellum. These brain areas are densely populated with cannabinoid receptors that attach to THC, the active ingredient in marijuana.
In mice, excessive marijuana use might damage parts of the brain and "knock out certain kinds of neurons," said Bolla. This can lead to receptors in the brain being over-stimulated or under-stimulated, changing their response to chemical messengers in the brain, similar to what might result from a brain injury.
Marijuana is the most widely used illicit drug in the US. An estimated 7 million people use marijuana weekly, according to 2000 data from the US Department of Health and Human Services.
This is only the second study to examine the residual effects of marijuana use after more than a couple of days of abstinence. Dr. Harrison Pope Jr., a professor of psychiatry at Harvard Medical School and author of the other study, found no difference in performance on cognitive tests between heavy marijuana users and "control" subjects.
Pope said in an interview that his "hunch" was that the difference between his results and Bolla's were the "sheer intensity" of marijuana use among the participants in Bolla's study. Heavy users in Pope's study smoked on average 1 or 1.5 joints over the course of a day.
According to Pope, people who smoke a lot of marijuana and start earlier will do worse on tests of mental function. Whether the toxicity of the drug itself is responsible, or factors like being in school less and being unfamiliar with testing or being more impaired initially and turning to pot for that reason, is difficult to know, he added.
SOURCE: Neurology 2002;59:1337-1343.
Let me make this perfectly clear - I've never ONCE called Liberteens - mice...
Puh-LEEZE! This is like one of those studies that found that saccharin causes cancer--if you drink a bathtub of it a day. They should give a medal to anyone whose lungs could stand 13 joints a day!
You know what Libertarians are good for don't you?
Neither does anyone else.
Is that some more proof?
Close. It's another article about pot, with another thread about libertarians. Somewhere, Pavlov is smiling.
I would think that they would perform somewhat less well on simple diagnostic tests than the control group.