Study: Long-Term Cannabis Use Not Associated With Changes In Brain Morphology

AUSTRALIA: The use of cannabis, even long-term, is not associated with changes in the cortical surface of the brain, according to data published in the journal European Neuropsychopharmacology.

A team of investigators from Australia and the Netherlands assessed the relationship between cannabis use and brain morphology in a cohort of 261 subjects (141 cannabis users and 120 controls). Researchers reported “no significant effects on cortical surface morphology” that could be attributable to subjects’ cannabis use, dependence, or age of initiation.

Authors concluded, “Our lack of finding in a well-powered study suggests that cortical surface morphology may be less associated with cannabis use than previously assumed.”

The findings are consistent with other recent brain imaging studies – such as those herehere, and here – and are largely inconsistent with those of a well-publicized 2014 study purporting that even causal cannabis exposure was linked to changes in the brain in young people.


For more information, contact Paul Armentano, NORML Deputy Director, at: paul@norml.org. Full text of the study, “Cortical surface morphology in long-term cannabis users: A multi-site MRI study,” appears in European Neuropsychopharmacology. Further information is available from the NORML fact-sheet, “Marijuana Exposure and Cognitive Performance.”

Study: Frequent Cannabis Use Unrelated To Brain Morphology

VIRGINIA:  The 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 wrote: “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.”

They concluded, “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 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.

A meta-analysis published last week 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.


For more information, contact Paul Armentano, NORML Deputy Director, at: paul@norml.org. Full text of the study, “Testing associations between cannabis use and subcortical volumes in two large population-based samples,” appears in Addiction. NORML’s online fact-sheet, “Marijuana Exposure and Cognitive Performance,” is available online.