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  • by Paul Armentano, NORML Deputy Director April 30, 2018

    Marijuana researchThe frequent use of cannabis is not associated with changes in brain structure, according to data published online ahead of print in the journal Addiction.

    An international team of scientists from Australia, the United Kingdom, and the United States assessed the relationship between habitual cannabis exposure and grey matter volumes in seven regions of the brain – including the thalamus, hippocampus, amygdala, and the nucleus accumbens – in two large population-based twin samples.

    Researchers reported, “[N]ormal variation in cannabis use is statistically unrelated to individual differences in brain morphology as measured by subcortical volume.”

    By contrast, the repeated use of nicotine was positively associated with significantly smaller thalamus volumes in middle-aged males.

    Authors concluded: “This is the largest exploratory analysis integrating brain imaging with self-report cannabis and comorbid substance use data. After correcting for multiple testing, there was no effect of cannabis use on the volume at any subcortical region of interest in young adults or middle-aged males. … In the context of expanding medicalization and decriminalization and the concerns surrounding the consequences of increased cannabis availability, our findings suggest that normal variation in cannabis use is statistically unrelated to brain morphology as measured by subcortical volumes in non-clinical samples.”

    The findings are consistent with those of prior brain imaging studies reporting that cannabis exposure appears to have little to no significant adverse impact upon brain morphology — particularly when compared to the dramatic effects associated with the alcohol exposure.

    The study’s findings fail to replicate those of a well-publicized 2014 paper which alleged that even casual marijuana exposure may be linked to brain abnormalities, particularly in the amygdala.

    Last week, a meta-analysis of 69 separate studies reported that cannabis exposure in adolescents and young adults is not associated with any significant, residual detrimental effects on cognitive performance. The results from a pair of recently published longitudinal twin studies similarly report that cannabis use is not independently associated with any residual change in intelligence quotient or executive function.

    An abstract of the study, “Testing associations between cannabis use and subcortical volumes in two large population-based samples,” appears online here.

  • by Paul Armentano, NORML Deputy Director September 6, 2011

    [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. To watch NORML’s weekly video summary of the week’s top stories, click here.]

    The administration of the synthetic cannabinoid agonist HU-211 decreases nerve cell death in an in vitro model of ethanol withdrawal, according to data published online in the journal of the Public Library of Science (PLoS ONE).

    An international team of researchers from France and Spain assessed the anti-excitotoxic effects of the synthetic cannabinoid HU-211 in culture. Researchers demonstrated that cannabinoid administration protected neurons from cell death in an experimental model of ethanol withdrawal. By contrast, the administration of a cannabinoid antagonist (rimonabant) during ethanol withdrawal greatly increased cell death.

    [T]hese observations show, for the first time, that the stimulation of the endocannabinoid system could be protective against the hyper-excitability developed during alcohol withdrawal,” investigators concluded. “By contrast, the blockade of the endocannabinoid system seems to be counterproductive during alcohol withdrawal.”

    In humans, the abrupt cessation of alcohol in dependent subjects may be associated with tremor, delirium, brain damage, and death.

    Separate pre-clinical studies have previously documented that administration of the non-psychotropic organic cannabinoid cannabidiol (CBD) in animals is neuroprotective against cerebral infarction and ethanol-induced neurotoxicity (alcohol poisoning).

    In 2009 and 2010, a pair of studies conducted by investigators at the University of California at San Diego reported that the consumption of cannabis may offset certain alcohol-induced brain abnormalities, including the loss of white matter integrity and impaired memory, in human subjects with a history of both alcohol and marijuana use.

    Full text of the study appears online in PLoS ONE here.

  • by Paul Armentano, NORML Deputy Director July 27, 2011

    [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.]

    The consumption of cannabis, even long-term, poses few adverse effects on cognitive performance, according to clinical trial data to be published in the scientific journal Addiction.

    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.