Smoking Marijuana Doesn’t Lead to Changes in the Hippocampus, Study Finds

AMSTERDAM, THE NETHERLANDS — The regular use of cannabis by young people is not associated with hippocampal volume alterations, according to case-control longitudinal data published online ahead of print in the Journal of Psychopharmacology.

Investigators from the Netherlands and the United Kingdom conducted magnetic resonance imaging (MRI) scans at baseline and at follow up (average of 39-months post-baseline) in 20 habitual cannabis users and in 23 non-using controls.

Authors reported: “Compared to controls, cannabis users did not show hippocampal volume alterations at either baseline or follow-up. Hippocampal volumes increased over time in both cannabis users and controls, following similar trajectories of increase. Cannabis dose and age of onset of cannabis use did not affect hippocampal volumes.”

They concluded, “Continued heavy cannabis use did not affect hippocampal neuroanatomical changes in early adulthood. … These data suggest that cannabis users show the same developmental trends as normative samples and that heavy cannabis use in this group may not necessarily interfere with hippocampal changes in neuroanatomy in early adulthood.”

The findings are consistent with other recent studies, such as those here and here, finding that the use of alcohol but not cannabis is negatively associated with specific structural changes in the developing brain.

Full text of the study, “Longitudinal study of hippocampal volumes in heavy cannabis users,” appears in The Journal of Psychopharmacology.

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