It was less than a year ago when the mainstream media was chock-full of headlines like this one: ‘Brain changes associated with casual marijuana use in young adults, study finds.’ The alarmist headlines were in response to a controversial paper published by researchers at Harvard University in Boston and Northwestern University in Chicago which alleged to have found differences in brain morphology in a cohort of 20 college-age marijuana users as compared to 20 non-users. The study’s investigators attributed the differences to subjects’ cannabis use.
But a funny thing happened when a team of scientists from the University of Colorado and the University of Kentucky tried to replicate these results in a separate, larger sample (158 participants) of subjects after rigorously controlling for both groups’ use of alcohol.
Writing in the January 28 edition of The Journal of Neuroscience, authors summarized:
“[T]his retrospective study examined brain morphology in a sample of adult daily marijuana users (n = 29) versus nonusers (n = 29) and a sample of adolescent daily users (n = 50) versus nonusers (n = 50). Groups were matched on a critical confounding variable, alcohol use, to a far greater degree than in previously published studies.
We acquired high-resolution MRI scans, and investigated group differences in gray matter using voxel-based morphometry, surface-based morphometry, and shape analysis in structures suggested to be associated with marijuana use, as follows: the nucleus accumbens, amygdala, hippocampus, and cerebellum.
No statistically significant differences were found between daily users and nonusers on volume or shape in the regions of interest. Effect sizes suggest that the failure to find differences was not due to a lack of statistical power, but rather was due to the lack of even a modest effect.”
Why the contradictory results? Investigators speculated that previously reported imaging studies failed to adequately control for the impact of alcohol, a substance that “unlike marijuana, … has been unequivocally associated with deleterious effects on brain morphology and cognition in both adults and adolescents.” In other words, researchers theorized that previously reported differences in the brain images of marijuana consumers as compared to non-users were likely because of subjects consumption of booze, not cannabis.
They concluded, “In sum, the results indicate that, when carefully controlling for alcohol use, gender, age, and other variables, there is no association between marijuana use and standard volumetric or shape measurements of subcortical structures. … [I]t seems unlikely that marijuana use has the same level of long-term deleterious effects on brain morphology as other drugs like alcohol. The press may not cite studies that do not find sensational effects, but these studies are still extremely important.”
An abstract of the study, “Daily Marijuana Use Is Not Associated with Brain Morphometric Measures in Adolescents or Adults,” is online here.
Newly appointed US Surgeon General Vivek Murthy believes that cannabis possesses therapeutic utility — an acknowledgment that contradicts the plant’s present placement as a Schedule I controlled substance under federal law.
Speaking to CBS News, Murthy said: “We have some preliminary data showing that for certain medical conditions and symptoms that marijuana can be helpful.” He added, “I think we have to use that data to drive policy making and I’m very interested to see where that data takes us.”
Dr. Murthy was confirmed as US Surgeon General late last year.
His statements appear to be inconsistent with the Schedule I classification of marijuana under federal law — a scheduling that defines the plant and its organic compounds as possessing “no currently accepted medical use …. in the United States” and lacking “accepted safety … under medical supervision.”
Next week in Sacramento, a federal judge will hear final arguments in a motion challenging the constitutionality of cannabis’ Schedule I classification. In October, defense counsel and experts presented evidence over a five day period arguing that the scientific literature is not supportive of the plant’s present categorization.
Briefs in this ongoing federal case are available online here.
[Update: Perhaps predictably, the Surgeon General has dialed back his initial comments to CBS News. Late last night, The Department of Health and Human Services issued a statement attributed to Murthy stating: “Marijuana policy — and all public health policies — should be driven by science. I believe that marijuana should be subjected to the same, rigorous clinical trials and scientific scrutiny that the Food and Drug Administration (FDA) applies to all new medications. The Federal Government has and continues to fund research on possible health benefits of marijuana and its components. While clinical trials for certain components of marijuana appear promising for some medical conditions, neither the FDA nor the Institute of Medicine have found smoked marijuana to meet the standards for safe and effective medicine for any condition to date.”
Interesting that Dr. Murthy cites the IOM which hasn’t formally commented on the issue of medical marijuana since releasing its report some 15 years ago, long before the results of FDA-approved clinical trials like this had been completed. Also notable that he leans on the FDA for guidance when the agency largely does not review the safety and efficacy of botanical products.]
Cannabis use is inversely associated with incidences of bladder cancer in males, according epidemiological findings published in the February issue of the journal Urology.
Investigators at the Kaiser Permanente Los Angeles Medical Center, Department of Neurology assessed the association of cannabis use and tobacco smoking on the risk of bladder cancer in a multiethnic cohort of more than 80,000 men aged 45 to 69 years old over an 11-year period.
Researchers determined that a history of cannabis use was associated with a decreased risk of bladder cancer. By contrast, tobacco use was associated with an increased risk of cancer.
“After adjusting for age, race or ethnicity, and body mass index, using tobacco only was associated with an increased risk of bladder cancer (hazard regression 1.52) whereas cannabis use was only associated with a 45 percent reduction in bladder cancer incidence (HR 0.55),” investigators reported.
Subjects who reported using both tobacco and cannabis possessed a decreased risk of cancer (HR 1.28) compared to those subjects who used tobacco only (HR 1.52).
The study is the first to indicate that cannabis use may be inversely associated with bladder cancer risk.
“In this multiethnic cohort of 82,050 men, we found that cannabis use alone was associated with a decreased risk of bladder cancer. … [M]en who used tobacco alone were 1.5 times more likely to develop bladder cancer when compared with men who did not use tobacco or cannabis. … However, among men who used both substances, this risk of bladder cancer was mitigated. … If this represents a cause and effect relationship, this pathway may provide new opportunities for the prevention and/or treatment of bladder cancer.”
In 2009, Brown University researchers similarly reported that the moderate long-term use of marijuana was associated with a reduced risk of head and neck cancers in a multi-center cohort involving over 1,000 subjects. Investigators further reported that marijuana use “modified the interaction between alcohol and cigarette smoking, resulting in a decreased HNSCC (head and neck squamous cell carcinoma) risk among moderate smokers and light drinkers, and attenuated risk among the heaviest smokers and drinkers.”
Read the abstract of the study, “Association between cannabis use and the risk of bladder cancer: Results from the California Men’s Health Survey,” online here.
Need another prime example of cannabis prohibition coming to pass in these United States? Look no further than the states of Alaska and Oregon where the voters have ended cannabis prohibition and instead replaced the failed prohibition with tax-n-regulate policies, both states are canceling the use (and expense) of maintaining and employing cannabis sniffing canines.
Up next in states that have jettisoned cannabis prohibition: Canceling law enforcement overflights looking for once illegal cannabis plants.
The inhalation of one marijuana cigarette per day over a 20-year period is not associated with adverse changes in lung health, according to data published online ahead of print in the journal Annals of the American Thoracic Society.
Investigators at Emory University in Atlanta assessed marijuana smoke exposure and lung health in a large representative sample of US adults age 18 to 59. Researchers reported that cannabis exposure was not associated with FEV1 (forced expiratory volume) decline or deleterious change in spirometric values of small airways disease.
Authors further reported that marijuana smoke exposure may even be associated with some protective lung effects among long-term smokers of tobacco. Investigators acknowledged, “[T]he pattern of marijuana’s effects seems to be distinctly different when compared to that of tobacco use.”
Researchers also acknowledged that habitual cannabis consumers were more likely to self-report increased symptoms of bronchitis, a finding that is consistent with previous literature. Separate studies indicate that subjects who vaporize cannabis report fewer adverse respiratory symptoms than do those who inhale combustive marijuana smoke.
Authors concluded, “[I]n a large representative sample of US adults, ongoing use of marijuana is associated with increased respiratory symptoms of bronchitis without a significant functional abnormality in spirometry, and cumulative marijuana use under 20 joint-years is not associated with significant effects on lung function.”
This study is the largest cross-sectional analysis to date examining the relationship between marijuana use and spirometric parameters of lung health.
A separate study published in 2012 in The Journal of the American Medical Association (JAMA) similarly reported that cumulative marijuana smoke exposure over a period of up to 7 joint-years (the equivalent of up to one marijuana cigarette per day for seven years) was not associated with adverse effects on pulmonary function.
A 2013 review also published in the Annals of the American Thoracic Society acknowledged that marijuana smoke exposure was not positively associated with the development of lung cancer, chronic obstructive pulmonary disease (COPD), emphysema, or bullous lung disease. It concluded: “[H]abitual use of marijuana alone does not appear to lead to significant abnormalities in lung function. Findings from a limited number of well-designed epidemiological studies do not suggest an increased risk of either lung or upper airway cancer from light or moderate use. … Overall, the risks of pulmonary complications of regular use of marijuana appear to be relatively small and far lower than those of tobacco smoking.”
You may view an abstract of the study, “Effects of marijuana exposure on expiratory airflow: A study of adults who participated in the US National Health and Nutrition Examination Study,” here.