Cannabinoids were more potent in older mice, and low doses had opposite effects in young versus old animals | Research

The takeaway

The synthetic cannabinoid CP55940 was more potent and effective in aged mice than young adults, with stronger pain relief and movement suppression. Low doses paradoxically stimulated movement in young mice but not in old mice.

Geriatricians, cannabis researchers studying age effects, and older adults considering cannabis.

Cannabinoids more potent in aged vs. young-adult mice

What the researchers found

CP55940 produced greater antinociception (pain relief) and locomotor inhibition in aged (21-24 month) compared to young-adult (4 month) mice. Low doses paradoxically stimulated movement in young mice (hormesis), but this effect was diminished in aged animals. Both CB1 and CB2 receptors mediated the effects.

Why it matters

Cannabis use among older adults is increasing rapidly, yet almost no preclinical data exist in aged models. The greater potency in older animals suggests that elderly users may need lower doses and face different risk profiles.

The numbers in context

Young-adult mice: 4 months old. Aged mice: 21-24 months old. Aged mice showed exaggerated antinociception and locomotor inhibition compared to young adults.

How the study worked

Young-adult and aged C57BL/6 mice received CP55940 at multiple doses. Locomotion, body temperature, thermal pain response (nociception), and fecal output were measured.

What this study cannot tell us

Animal study using a synthetic cannabinoid (not THC or CBD). Mouse aging does not perfectly model human aging. Only male and female mice of two age groups were compared.

How to read the evidence

Preliminary: animal study comparing two age groups with a synthetic cannabinoid.

When this study was published

Published in 2020 in npj Aging and Mechanisms of Disease.

The bigger picture

The age-dependent difference in cannabinoid response has direct clinical relevance as more seniors use cannabis for pain and other conditions. Standard dosing recommendations developed in younger populations may be inappropriate for elderly users.

Questions still open

Do human seniors also show heightened sensitivity to cannabinoids? Should cannabis dosing guidelines be age-adjusted? What changes in the endocannabinoid system explain the age difference?

Common questions

Why are cannabinoids more potent in older animals?

The study found the effect but did not fully explain the mechanism. Possible reasons include age-related changes in cannabinoid receptor density, altered endocannabinoid levels, or changes in drug metabolism in older animals.

What is the hormesis effect?

At low doses, CP55940 paradoxically stimulated movement in young mice rather than suppressing it. This bidirectional dose effect was largely absent in aged mice, suggesting the endocannabinoid system responds differently to low-dose stimulation as it ages.

Read the original research

Age-dependent hormesis-like effects of the synthetic cannabinoid CP55940 in C57BL/6 mice.

NPJ aging and mechanisms of disease, 6, 7

View on PubMed ↗Publisher’s paper ↗

Citation

Hodges, Erik L; Marshall, Jessica P; Ashpole, Nicole M. (2020). Age-dependent hormesis-like effects of the synthetic cannabinoid CP55940 in C57BL/6 mice.. NPJ aging and mechanisms of disease, 6, 7. https://doi.org/10.1038/s41514-020-0045-7