THC upregulated an anxiety-linked dopamine receptor complex (D1-D2 heteromer) in adult but not adolescent rats and monkeys, which may explain why teens experience less negative affect from cannabis — potentially promoting continued use.
Read this if you are a parent, educator, or clinician concerned about adolescent cannabis use and want to understand the neuroscience behind teen vulnerability.
Age-specific effectTHC upregulated aversive D1-D2 receptors in adults but not adolescents
What the researchers found
Adolescent rats had lower baseline levels of D1-D2 receptor heteromers than adults. Repeated THC administration upregulated D1-D2 heteromers in adult rat striatum but not in adolescent rat or monkey brain. Adult rats treated with THC showed anxiety and anhedonia-like behavior that correlated with D1-D2 density, while adolescent rats did not. Co-administration of CBD with THC prevented D1-D2 upregulation. A CB1 receptor inverse agonist also blocked the effect, confirming cannabinoid system involvement.
Why it matters
This study provides a biological mechanism for a well-known paradox: adolescents seem less sensitive to THC's negative emotional effects, which may make them more likely to continue using cannabis. The absence of an "aversive brake" in the adolescent brain could increase vulnerability to long-term cannabis dependence.
The numbers in context
- Adolescent rats had lower baseline striatal D1-D2 heteromer density vs adults
- THC upregulated D1-D2 in adult but not adolescent rat striatum
- THC upregulated D1-D2 in adult rat nucleus accumbens and dorsal striatum
- CBD co-administration prevented D1-D2 upregulation
- CB1 inverse agonist attenuated D1-D2 upregulation
How the study worked
Repeated THC administration to adolescent monkeys and both adolescent and adult rats. Measured D1-D2 heteromer expression in striatal regions using immunological methods. Behavioral testing for anxiety and anhedonia. Tested CBD co-administration and CB1 receptor inverse agonist.
Who was studied
Adolescent and adult rats; adolescent monkeys
What this study cannot tell us
Animal study that may not directly translate to human brain development. The adolescent window in rats is brief and may not perfectly model human adolescence. Behavioral measures in rodents are proxies for human emotional states.
How to read the evidence
Preclinical animal study in rats and monkeys with robust methodology including cross-species validation and pharmacological controls.
When this study was published
Published in 2023. Addresses a critical question in adolescent cannabis neuroscience.
The bigger picture
Understanding why adolescents are more vulnerable to cannabis dependence is critical for prevention efforts. If THC lacks the aversive signaling in teen brains that naturally limits use in adults, targeted prevention messaging should emphasize that feeling less anxious from cannabis as a teen is not a sign of safety — it may be a sign of greater risk.
Questions still open
- Would CBD-dominant products be safer for adolescents since CBD prevents D1-D2 upregulation?
- At what age does the D1-D2 heteromer system mature to adult levels in humans?
- Could the D1-D2 receptor complex be a biomarker for vulnerability to cannabis use disorder?
Read the original research
Δ9-Tetrahydrocannabinol does not upregulate an aversive dopamine receptor mechanism in adolescent brain unlike in adults.
Current research in neurobiology, 5, 100107
Citation
Di Raddo, Marie-Eve; Milenkovic, Marija; Sivasubramanian, Meenalochani; Hasbi, Ahmed; Bergman, Jack; Withey, Sarah; Madras, Bertha K; George, Susan R. (2023). Δ9-Tetrahydrocannabinol does not upregulate an aversive dopamine receptor mechanism in adolescent brain unlike in adults.. Current research in neurobiology, 5, 100107. https://doi.org/10.1016/j.crneur.2023.100107