[Editor's note: This post is excerpted from this week's forthcoming NORML weekly media advisory. To have NORML's media alerts and legislative advisories delivered straight to your in-box, sign up here.]
Investigators at the University of Melbourne and the Australian National University, Center for Mental Health Research assessed the impact of cannabis use on various measures of memory and intelligence in over 2,000 self-identified marijuana consumers and non-users over an eight-year period. Among cannabis consumers, subjects were grouped into the following categories: ‘heavy’ (once a week or more) users, ‘light’ users, ‘former heavy’ users, ‘former light’ users, and ‘always former’ — a category that consisted of respondents who had ceased using marijuana prior to their entry into the study.
Researchers reported: “Only with respect to the immediate recall measure was there evidence of an improved performance associated with sustained abstinence from cannabis, with outcomes similar to those who had never used cannabis at the end point. On the remaining cognitive measures, after controlling for education and other characteristics, there were no significant differences associated with cannabis consumption.”
They concluded, “Therefore, the adverse impacts of cannabis use on cognitive functions either appear to be related to pre-existing factors or are reversible in this community cohort even after potentially extended periods of use.”
Separate studies have previously reported that long-term marijuana use is not associated with residual deficits in neurocognitive function. Specifically, a 2001 study published in the journal Archives of General Psychiatry found that chronic cannabis consumers who abstained from the drug for one week “showed virtually no significant differences from control subjects (those who had smoked marijuana less than 50 times in their lives) on a battery of 10 neuropsychological tests. … Former heavy users, who had consumed little or no cannabis in the three months before testing, [also] showed no significant differences from control subjects on any of these tests on any of the testing days.”
Additionally, studies have also implied that cannabis may be neuroprotective against alcohol-induced cognitive deficits. A 2009 study by investigators at the University of California and San Diego reported that binge drinkers who also used cannabis experienced significantly less white matter damage to the brain as compared to subjects who consumed alcohol alone.
For more information regarding the impact of cannabis on brain function, see NORML’s factsheet ‘Cannabis and the Brain: A User’s Guide,’ here.
UPDATE!!! In a 12/29 e-mail communication with the San Diego Union-Tribune‘s Newsroom Operations Manager (in reference to their coverage below), she pledges: “I will follow up with our online staff right now. We will get it corrected or taken down.” Yet, as of 11am pst today the story still appears online in its original form. Those who live in southern California may also wish to voice their opinion at: http://www.signonsandiego.com/contactus/.
For anyone who missed the worldwide corporate media’s hysterical anti-pot headlines last week, here’s a sampling:
Cannabis more damaging to adolescent brains than previously known
via Emax Health
“New research shows that teens who consume cannabis daily can suffer anxiety and depression. Smoking marijuana can have long-term irreversible effects on adolescent brains, and is more harmful to teens than previously known.”
Teen marijuana use affects brain permanently: study
via CBC News
“The findings suggest daily marijuana use by teens can cause depression and anxiety, and have an irreversible effect on the brain.”
Pot damage on teens worse than thought
via UPI wire services
“Daily consumption of marijuana in teens can cause depression and anxiety, and have irreversible long-term effect on the brain, Canadian researchers say.”
Cannabis brain damage worse in teens than thought: study
via The Canadian Press
“The effects of daily cannabis use on teenage brains is worse than originally thought, and the long-term effects appear to be irreversible, new research from McGill University suggests.”
Sounds scary, huh? It’s meant to. Only there’s three serious problems with the mainstream media’s alarmist coverage.
1) No adolescents — or for that matter, any human beings whatsoever — actually participated in the study.
2) No actual cannabis was consumed in the study.
3) No permanent brain damage was reported in the study.
Don’t believe me? Well then, check out the actual source of the headlines yourself.
“We tested this hypothesis by administering the CB(1) receptor agonist WIN55,212-2, once daily for 20 days to adolescent and adult rats. … Chronic adolescent exposure but not adult exposure to low (0.2 mg/kg) and high (1.0 mg/kg) doses led to depression-like behaviour in the forced swim and sucrose preference test, while the high dose also induced anxiety-like consequences in the novelty-suppressed feeding test. … These (findings) suggest that long-term exposure to cannabinoids during adolescence induces anxiety-like and depression-like behaviours in adulthood and that this may be instigated by serotonergic hypoactivity and noradrenergic hyperactivity.”
To summarize: Investigators administered daily doses of a highly potent synthetic cannabinoid receptor agonist WIN,55,212-2 to both adolescent rats and adult rats for 20 days. Days following their exposure, researchers documented altered serotonin production in younger rats. (Why investigators presumed that the change in serotonin production would be permanent I have no idea. After the initial 20-day waiting period, researchers do not appear to have tested the rats’ serotonin levels ever again.) Researchers also documented supposed depression-like and anxiety-like behavior in certain rats, based on various elaborate animal models and preference tests.
Yet somehow based on this speculative preclinical evidence, the mainstream media — in unison — proclaimed:
via San Diego Tribune
“A study of Canadian teenagers … found that smoking the illicit drug is harder on young brains than originally thought. Writing in the journal Neurobiology of Disease, researchers at McGill University in Montreal said daily consumption of cannabis in teens can cause significant depression and anxiety and have an irreversible long-term effect on the brain.”
In truth, the purported ‘study’ never said anything of the sort!
So why the does the MSM consistently get the story wrong when it comes to pot? You can check out my previous thoughts on the issue here.
Apparently my latest missive has hit a nerve — as it has quickly risen to become the most read story on Alternet.
5 Things the Corporate Media Don’t Want You to Know About Cannabis
1. Marijuana Use Is Not Associated With a Rise in Incidences of Schizophrenia
2. Marijuana Smoke Doesn’t Damage the Lungs Like Tobacco
3. Cannabis Use Potentially Protects, Rather Than Harms, the Brain
4. Marijuana Is a Terminus, Not a ‘Gateway,’ to Hard Drug Use
5. Government’s Anti-Pot Ads Encourage, Rather Than Discourage, Marijuana Use
Read the full text of the story here.
[Editor's note: This post is excerpted from this week's forthcoming NORML weekly media advisory. To have NORML's media advisories delivered straight to your in-box, sign up for NORML's free e-zine here.]
The consumption of cannabis, even long-term, has a “minimal” impact on brain function, according to a systematic literature review just published online by the journal Psychological Medicine.
An international team of investigators from the United Kingdom, Spain, Brazil, Australia, and Switzerland conducted a systematic review of the effects of cannabis on brain structure and function.
Authors wrote, “We reviewed literature reporting neuroimaging studies of chronic or acute cannabis use published up until January 2009. … Sixty-six studies were identified, of which 41 met the inclusion criteria. Thirty-three were functional (SPECT/PET/fMRI) and eight structural (volumetric/DTI) imaging studies. … Only three of the structural imaging studies found differences between users and controls.”
Investigators concluded, “Minimal evidence of major effects of cannabis on brain structure has been reported,” noting that marijuana users and controls perform similarly on cognitive tasks.
According to a 2001 study published in the journal Archives of General Psychiatry, long-term cannabis smokers who abstained from pot for one week “showed virtually no significant differences from control subjects (those who had smoked marijuana less than 50 times in their lives) on a battery of 10 neuropsychological tests.” Investigators added, “Former heavy users, who had consumed little or no cannabis in the three months before testing, [also] showed no significant differences from control subjects on any of these tests on any of the testing days.”
Ever wonder why the studies purporting to ‘prove’ marijuana’s health risks only recruit subjects who smoke pot 24 hours a day, seven days a week?
Heavy marijuana use shrinks brain parts
Brain scans showed the hippocampus and amygdala were smaller in men who were heavy marijuana users compared to nonusers. … The men had smoked at least five marijuana cigarettes daily for on average 20 years.
The answer: If they didn’t, there wouldn’t be any purported risks left to write about.
I mean, seriously, imagine if these scientists had tried recruiting 15 subjects who drank at least five shots of vodka every day for 20 years? That is, if they could find 15 subjects who were still alive.
Marijuana may up heart attack, stroke risk
Heavy marijuana use can boost blood levels of a particular protein, perhaps raising a person’s risk of a heart attack or stroke, U.S. government researchers said on Tuesday. …The marijuana users in the study averaged smoking 78 to 350 marijuana cigarettes per week.
The study did not look at whether the heavy marijuana users actually had heart disease.
So here we go again. Three-hundred and fifty joints per week?! Who are these people? And what’s with the caveat at the end of the story? If the purpose of the study is to assess whether there might be a link between ridiculously heavy pot use and heart disease, then why not, you know, look to see whether the subjects actually suffered from heart disease? (Likely answer: Aside from the abnormal protein level, the patients were probably otherwise healthy.)
Bottom line: smoking pot all day, every day probably isn’t good for you (though I find it interesting that, even among the most prolific pot users, most of the herb’s purported dangers are either speculative or are only apparent on hyper-sensitive brain scans and multi-tiered neurocognitive tests). Fortunately, 99.9 percent of pot smokers don’t behave this way.
And no, it’s not prohibition that curbs their use habits; it’s the recognition that too much pot is not conducive to an otherwise healthy, responsible lifestyle (just as pounding five shots a day wouldn’t be conducive to, well, life).
So what lesson can be learned from the two studies above (aside from the fact that our government has no interest in investigating the health of ordinary cannabis consumers)? It’s that pot, like alcohol, is best consumed in moderation, and that pot prohibition — even when compared to the excessive use of the drug itself — still poses the greatest threat to health.