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How long-term cannabis use impacts midlife cognition and hippocampal volume

By Scott Cunningham, MD, PhD
Published June 17, 2022

Key Takeaways

  • Long-term cannabis use is associated with midlife cognitive deficits and decreased hippocampal volume, which has a high density of CB1 receptors.

  • Both cognitive deficits and decreased hippocampal volume are known risk factors for dementia.

Putting It Into Practice

Cannabis use is on the rise due to increasing legalization for recreational and medical use. Psychoactive drugs, including cannabis, have short- and long-term effects on cognition, especially memory, attention, and processing.

The varying effects of cannabis on cognition and brain structures based on age, frequency of use, age at onset of use, duration of effect, and individual constituents warrant continued investigation.

Why this study matters

There is no debate that acute cannabis intoxication impairs cognitive function, and now there is evidence that chronic cannabis use leads to persistent cognitive deficits that have a neuroanatomic basis.

Study design

The study population (n=1037) was born in 1972-3 and followed to age 45 years. Cannabis use was determined at ages 18, 21, 26, 32, 38, and 45 years. Neuropsychological testing was performed and hippocampal volume was determined at age 45.

Results and conclusion

Long-term cannabis use was associated with the following compared to tobacco, alcohol, and recreational cannabis users: decreased IQ (-5.5 points from childhood-to-midlife); poor learning and processing speed; and memory and attention deficits.

Moreover, the hippocampal volume was decreased in long-term cannabis users.

Original Source

Meier MH, Caspi A, R. Knodt A, et al. Long-term cannabis use and cognitive reserves and hippocampal volume in midlife. Amer J Psych 2022;179:362-74.

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