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executive function

  • 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 November 14, 2016

    Marijuana researchMedical cannabis administration is associated with improved cognitive performance and lower levels of prescription drug use, according to longitudinal data published online in the journal Frontiers in Pharmacology.

    Investigators from Harvard Medical School, Tufts University, and McLean Hospital evaluated the use of medicinal cannabis on patients’ cognitive performance over a three-month period. Participants in the study were either naïve to cannabis or had abstained from the substance over the previous decade. Baseline evaluations of patients’ cognitive performance were taken prior to their cannabis use and then again following treatment.

    Researchers reported “no significant decrements in performance” following medical marijuana use. Rather, they determined, “[P]atients experienced some improvement on measures of executive functioning, including the Stroop Color Word Test and Trail Making Test, mostly reflected as increased speed in completing tasks without a loss of accuracy.”

    Participants in the study were less likely to experience feelings of depression during treatment, and many significantly reduced their use of prescription drugs. “[D]ata revealed a notable decrease in weekly use across all medication classes, including reductions in use of opiates (-42.88 percent), antidepressants (-17.64 percent), mood stabilizers (-33.33 percent), and benzodiazepines (-38.89 percent),” authors reported – a finding that is consistent with prior studies.

    Patients in the study will continue to be assessed over the course of one-year of treatment to assess whether these preliminary trends persist long-term.

    Full text of the study, “Splendor in the grass? A pilot study assessing the impact of marijuana on executive function,” appears online here.