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: Inhaled Cannabis Augments Analgesic Efficacy Of Opiates

NEW YORK: The co-administration of inhaled cannabis and sub-therapeutic doses of oxycodone produces enhanced analgesic effects in human subjects, according to clinical trial data published in the journal Neuropsychopharmacology.

A team of investigators from the United States and Australia assessed the efficacy of inhaled cannabis and low doses of oxycodone on experimentally-induced pain in a double-blind, placebo-controlled model. Researchers assessed subjects’ pain tolerance after receiving both substances separately or in concert with one another.

While neither the administration of cannabis nor oxycodone alone significantly mitigated subjects’ pain, the combined administration of both drugs did so effectively. Authors determined, “Both active cannabis and a low dose of oxycodone (2.5 mg) were sub-therapeutic, failing to elicit analgesia on their own; however, when administered together, pain responses … were significantly reduced, pointing to the opioid-sparing effects of cannabis.”

They concluded, “Smoked cannabis combined with an ineffective analgesic dose of oxycodone produced analgesia comparable to an effective opioid analgesic dose without significantly increasing cannabis’s abuse liability.”

The findings are similar to those of a 2011 clinical trial determining that vaporized cannabis interacts synergistically with opioids to induce pain relief and therefore “may allow for opioid treatment at lower doses with fewer side effects.”

In jurisdictions where marijuana is legally available, patients frequently acknowledge reducing their use of conventional medications, particularly opioids and benzodiazepines, after engaging in cannabis therapy.


For more information, contact Paul Armentano, NORML Deputy Director, at: paul@norml.org. Full text of the study, “Impact of co-administration of oxycodone and smoked cannabis on analgesia and abuse liability,” appears in Neuropsychopharmacology.