Daily THC during adolescence did not permanently alter pain responses in adult mice | Research

The takeaway

Mice given daily THC injections throughout adolescence showed no lasting changes in pain sensitivity, morphine pain relief effectiveness, or morphine tolerance development when tested as adults.

Pain researchers, adolescent health professionals, and anyone interested in the long-term effects of teenage cannabis exposure.

No lasting pain processing changes after daily adolescent THC in either sex

What the researchers found

Adolescent mice receiving daily THC (5 mg/kg) from postnatal day 30-43 showed no significant differences from controls in formalin-induced pain behavior, chronic nerve injury pain responses, morphine antinociception, or morphine tolerance when tested at postnatal day 70. This held true for both male and female mice.

Why it matters

Concerns about adolescent cannabis use often focus on lasting brain changes. This study specifically tested whether adolescent THC exposure permanently alters pain processing circuits, finding no evidence of lasting disruption at a moderate dose.

The numbers in context

THC dose: 5 mg/kg daily; treatment window: PND 30-43 (adolescence); testing at PND 70 (adulthood); both sexes tested; no significant differences on any pain measure

How the study worked

C57BL6/J mice of both sexes received daily THC (5 mg/kg, i.p.) or vehicle throughout adolescence (PND 30-43). At adulthood (PND 70), researchers assessed pain behavior using the formalin test and chronic constriction injury model, and morphine responses using the tail immersion test.

What this study cannot tell us

Single moderate dose tested; higher or more frequent doses might yield different results. Mouse adolescence is a rough analog to human adolescence. Only pain outcomes examined; other cognitive or psychiatric effects were not assessed.

How to read the evidence

Well-controlled animal study with multiple pain models and both sexes, but single dose level and inherent limitations of mouse-to-human translation.

When this study was published

Published in 2021.

The bigger picture

While adolescent THC exposure has been linked to changes in other brain systems, this study suggests pain processing circuits may be more resilient. The finding adds important nuance to the conversation about long-term consequences of adolescent cannabis use.

Questions still open

Would higher THC doses or longer exposure periods produce lasting pain processing changes? Do these results hold across different mouse strains? Could there be subtle effects on pain processing that these tests did not capture?

Common questions

Does this mean adolescent cannabis use is safe?

This study only examined pain processing. Adolescent THC exposure has been associated with changes in other brain systems, including cognition and mental health, which were not assessed here.

Were male and female mice affected differently?

No. Neither male nor female mice showed lasting changes in pain responses after adolescent THC exposure.

Read the original research

Persistent Exposure to Δ9-Tetrahydrocannabinol during Adolescence Does Not Affect Nociceptive Responding in Adult Mice.

The Journal of pharmacology and experimental therapeutics, 378(3), 215-221

View on PubMed ↗Publisher’s paper ↗

Citation

Mabou Tagne, Alex; Fotio, Yannick; Ibne Rashid, Tarif; Piomelli, Daniele. (2021). Persistent Exposure to Δ9-Tetrahydrocannabinol during Adolescence Does Not Affect Nociceptive Responding in Adult Mice.. The Journal of pharmacology and experimental therapeutics, 378(3), 215-221. https://doi.org/10.1124/jpet.121.000740