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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 January 2, 2018

    Legalization in DCNeither the occasional nor the heavy use of marijuana by adolescents is associated with decreased motivation, according to clinical data published online ahead of print in the journal Substance Use & Misuse.

    A team of Florida International University researchers assessed the relationship between cannabis use and motivation in 79 adolescent subjects. Participants consisted of both long-term regular consumers and occasional users. Investigators assessed subjects’ motivational tendencies through the use of two validated tools, the Apathy Evaluation Scale and the Motivation and Engagement Scale.

    Authors reported: “After controlling for confounds, no significant differences were observed between regular and light users on any motivation index. Similarly, no associations between motivation and lifetime or past 30-day cannabis use amount were observed.”

    They concluded, “Our findings do not support a link between reduced motivation and CU among adolescents after controlling for relevant confounds.”

    An abstract of the study, “Is cannabis use associated with various indices of motivation among adolescents?”, appears here.

  • by Paul Armentano, NORML Deputy Director August 3, 2017

    Marijuana researchCannabis use by teens is not independently linked with adverse changes in intelligence quotient or executive functioning, according to longitudinal data published online ahead of print in the journal Addiction.

    A team of investigators from the United States and the United Kingdom evaluated whether marijuana use is directly associated with changes over time in neuropsychological performance in a nationally representative cohort of adolescent twins. Authors reported that “family background factors,” but not the use of cannabis negatively impacted adolescents’ cognitive performance.

    They wrote: “[W]e found that youth who used cannabis … had lower IQ at age 18, but there was little evidence that cannabis use was associated with IQ decline from age 12 to 18. Moreover, although cannabis use was associated with lower IQ and poorer executive functions at age 18, these associations were generally not apparent within pairs of twins from the same family, suggesting that family background factors explain why adolescents who use cannabis perform worse on IQ and executive function tests.”

    Investigators concluded, “Short-term cannabis use in adolescence does not appear to cause IQ decline or impair executive functions, even when cannabis use reaches the level of dependence.”

    Their findings are consistent with those of several other studies – including those here, here, here, and here – finding that cannabis use alone during adolescence does not appear to have a significant, direct adverse effect on intelligence quotient.

    widely publicized and still often cited New Zealand study published in 2012 in The Proceedings of the National Academy of Sciences reported that the persistent use of cannabis from adolescence to adulthood was associated with slightly lower IQ by age 38. However, a follow up review of the data published later in the same journal suggested that the observed changes were likely due to socioeconomic differences, not the subjects’ use of cannabis. A later study by the initial paper’s lead investigator further reported that the effects of persistent adolescent cannabis use on academic performance are “non-significant after controlling for persistent alcohol and tobacco use.”

  • by Paul Armentano, NORML Deputy Director July 11, 2017

    marijuana_seedlingAlcohol consumption is associated with negative changes in gray matter volume and in white matter integrity, while cannabis use is not, according to data published online ahead of print in the journal Addiction.

    Investigators from the University of Colorado, Boulder and the Oregon Health & Science University evaluated neuroimaging data among adults (ages 18 to 55) and adolescents (ages 14 to 18). Authors identified an association between alcohol use and negative changes in brain structure, but identified no such association with cannabis.

    “Alcohol use severity is associated with widespread lower gray matter volume and white matter integrity in adults, and with lower gray matter volume in adolescents,” they concluded. By contrast, “No associations were observed between structural measures and past 30-day cannabis use in adults or adolescents.”

    Researchers acknowledged that their findings were similar to those of prior studies “suggesting that regionally specific differences between cannabis users and non-users are often inconsistent across studies and that some of the observed associations may actually be related to comorbid alcohol use.”

    A 2015 brain imaging study published in The Journal of Neuroscience similarly reported that cannabis use was not positively associated with adverse changes in the brain, but that alcohol “has been unequivocally associated with deleterious effects on brain morphology and cognition in both adults and adolescents.”

    Longitudinal data published in June in the British Medical Journal reported, “Alcohol consumption, even at moderate levels, is associated with adverse brain outcomes including hippocampal atrophy.”

    An abstract of the study, “Structural Neuroimaging Correlates of Alcohol and Cannabis Use in Adolescents and Adults,” appears online here.

  • by Paul Armentano, NORML Deputy Director April 27, 2017

    Cannabis PenaltiesA recently released white paper published by the National District Attorneys Association is calling for the federal government to strictly enforce anti-cannabis laws in states that have regulated its production and distribution for either medical or recreational purposes.

    The working group, which consists of D.A.s and prosecutors from more than a dozen states (including representatives from adult use states like California and Colorado), hopes to influence the Trump administration to set aside the 2013 Cole memorandum. That memorandum, authored by former US Deputy Attorney General James Cole, directs state prosecutors not to interfere with state legalization efforts and those licensed to engage in the plant’s production and sale, provided that such persons do not engage in marijuana sales to minors or divert the product to states that have not legalized its use, among other guidelines.

    “To maintain respect for the rule of law, it is essential that federal drug enforcement policy regarding the manufacture, importation, possession, use and distribution of marijuana be applied consistently across the nation,” the NDAA paper concludes.

    Predictably, authors repeat numerous falsehoods about marijuana and marijuana policy in an effort to bolster their call for a federal crackdown. Specifically, authors allege that cannabis damages the brain to a far greater extent than alcohol and that statewide regulations have increased young people’s access to the plant. Both claims are demonstrably false.

    The NDAA opines, “[Marijuana] is not like alcohol … because alcohol use does not cause the same type of permanent changes to teens’ ability to concentrate and learn.” Yet, well controlled studies dismiss the contention that cannabis exposure causes permanent structural damage to the brain.

    Specifically, a 2015 study assessed brain morphology in both daily adult and adolescent cannabis users compared to non-users, with a particular focus on whether any differences were identifiable in the nucleus accumbens, amygdala, hippocampus, and the cerebellum. Investigators reported “no statistically significant differences … between daily users and nonusers on volume or shape in the regions of interest” after researchers controlled for potentially confounding variables. In contrast to marijuana, researchers acknowledged that alcohol “has been unequivocally associated with deleterious effects on brain morphology and cognition in both adults and adolescents.”

    The NDAA further claims, “Legalization of marijuana for medical use and recreational use clearly sends a message to youth that marijuana is not dangerous and increases youth access to marijuana.”

    But data from the US Centers for Disease control reports that young people’s access to marijuana has fallen by 13 percent since 2002. The agency further reports, “Since 2002, the prevalence of marijuana use and initiation among U.S. youth has declined” – a finding that is consistent with numerous prior studies.

    Moreover, state-specific post-legalization data published in March by the Colorado Department of Public Health concludes: “[M]arijuana use, both among adults and among youth, does not appear to be increasing to date. No change was observed in past 30-day marijuana use among adults between 2014 (13.6 percent) and 2015 (13.4 percent). Similarly, there was no statistically significant change in 30-day or lifetime marijuana use among high school students between 2013 (lifetime: 36.9 percent, 30-day: 19.7 percent) and 2015 (lifetime: 38.0 percent, 30-day: 21.2 percent).” 2016 data compiled by Washington State Department of Social and Health Services similarly finds that “rates of teen marijuana use have remained steady” post legalization.

    The National District Attorneys Association is the largest and oldest prosecutor organization in the country. Their mission is to be “the voice of America’s prosecutors and strives to support their efforts to protect the rights and safety of the people in their communities.”

    The full text of the their paper, entitled “Marijuana Policy: The State and Local Prosecutors’ Perspective,” is available online here.

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