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Cannabis Use Not Associated with Negative Changes in Brain Structure, Study Finds

Alcohol consumption, but not cannabis use, is linked to adverse changes in brain structure, according to findings in a new study.

Using cannabis will not cause negative changes to the structure of the brain, suggest findings in a new study published in the peer-reviewed scientific journal Addiction.

Researchers from the University of Colorado, Boulder and the Oregon Health & Science University investigated neuroimaging data among adults between the ages of 18 and 55 years and adolescents between the ages of 14 to 18 years that use alcohol or marijuana. They found alcohol consumption to be associated with lower gray matter volume and poorer white matter integrity.

These negative structural measures, however, were not observed in the adults and adolescents that had used cannabis within the past 30 days.

Present in the brain, brainstem, cerebellum, and spinal cord, gray matter serves to process information in the brain. It is where all synapses are located, and therefore contains cell bodies, dendrites and axon terminals. White matter is found within the inner layer of the brain cortex and is mainly composed of long-range myelinated axons that are responsible for connecting different parts of grey matter to each other. Studies have found there to be a association with gray and white matter volume and general intelligence, memory, attention, and language.

The ability to draw definitive conclusions about the long-term impact of cannabis use on the human brain has been difficult so far, due to study participants in most cases using multiple substances. While imaging studies of the impact of the use of substances on brain structure have shown conflicting results, these new findings suggest that alcohol, rather than cannabis, may be behind any structural changes in the brain.

Medical Marijuana Research

According to the researchers, previous studies using brain imaging to examine the effects of alcohol and cannabis use have had similar findings, “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 study published earlier this year in the British Medical Journal found that “alcohol consumption, even at moderate levels, is associated with adverse brain outcomes including hippocampal atrophy.”

In 2015, researchers from the University of Colorado at Boulder and the University of Louisville in Kentucky similarly found cannabis use to not be linked to 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.”

Those researchers concluded that, “[I]t seems unlikely that marijuana use has the same level of long-term deleterious effects on brain morphology as other drugs like alcohol. … The press may not cite studies that do not find sensational effects, but these studies are still extremely important.”

The latest study, “Structural Neuroimaging Correlates of Alcohol and Cannabis Use in Adolescents and Adults,” is available to access via Wiley Online Library.

Learn more about the previous research into cannabis by visiting our education page. Keep up with the latest cannabis-related studies through our news feed.