Neuroscience Does Not Support Raising the Cannabis Legal Age to 25
A critical examination of the "brain matures at 25" claim finds no empirically defined neurodevelopmental endpoint at that age and no evidence that cannabis causes greater long-term harm in 18-25-year-olds compared to older adults.
Quick Facts
What This Study Found
While brain development continues into the third decade, there is no empirically defined endpoint at age 25. Brain maturation is nonlinear, region-specific, and influenced by sex. Existing evidence does not demonstrate greater long-term cognitive or neurophysiological harm from cannabis in individuals aged 18-25 compared to those over 25. An MLA of 18-21 is scientifically supportable.
Key Numbers
Current legal age limits range from 18-21 across jurisdictions. Some advocates propose age 25. Major brain structural development occurs early in life. Synaptic pruning and prefrontal changes continue through adolescence with subtle changes into the 20s.
How They Did This
Perspective/commentary examining neuroscientific evidence on brain development and its implications for setting legal cannabis age limits. Reviews macrostructural and microstructural brain development, synaptic pruning, gene expression, and prefrontal cortical changes.
Why This Research Matters
The "brain doesn't mature until 25" claim has become a popular argument for raising cannabis legal ages, but this review finds it oversimplifies neurodevelopmental science. Policy decisions based on a mythologized age threshold may create more harm (through criminalization of young adults) than they prevent.
The Bigger Picture
Setting legal thresholds requires balancing neuroscience with legal, social, and justice considerations. A policy that criminalizes 22-year-olds for cannabis use based on a misrepresented neuroscience claim could cause more harm to young adults than the cannabis exposure it aims to prevent.
What This Study Doesn't Tell Us
This is a perspective piece, not a systematic review. The authors argue a specific policy position, which inherently involves value judgments beyond pure science. Brain development research is ongoing and new findings could shift the evidence.
Questions This Raises
- ?Would an age-graduated system (e.g., lower THC potency limits for 18-21) be a better approach than a hard cutoff?
- ?How do justice system harms from criminalization of young adult cannabis use compare to potential neurological harms?
Trust & Context
- Key Stat:
- No empirically defined neurodevelopmental endpoint exists at age 25
- Evidence Grade:
- Moderate: well-argued perspective grounded in neuroscience literature, but a commentary rather than a systematic evidence synthesis.
- Study Age:
- 2025 perspective.
- Original Title:
- Challenging the 25-year-old 'mature brain' mythology: implications for the minimum legal age for non-medical cannabis use.
- Published In:
- The American journal of drug and alcohol abuse, 51(5), 577-583 (2025)
- Authors:
- Adinoff, Bryon(2), Nunes, Julio C(3)
- Database ID:
- RTHC-05869
Evidence Hierarchy
Summarizes existing research on a topic.
What do these levels mean? →Frequently Asked Questions
Does the brain stop developing at 25?
No. Brain development is a continuous, lifelong process. While major structural changes occur early in life and synaptic pruning continues through adolescence, there is no discrete endpoint at 25. Changes become more subtle in the 20s but do not simply stop at any single age.
Is cannabis safer after age 25?
The available evidence does not show that cannabis use between ages 18-25 causes greater long-term cognitive harm than use after 25. The "25 threshold" has been oversimplified from neuroscience research that actually shows gradual, nonlinear development without a clear cutoff.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-05869APA
Adinoff, Bryon; Nunes, Julio C. (2025). Challenging the 25-year-old 'mature brain' mythology: implications for the minimum legal age for non-medical cannabis use.. The American journal of drug and alcohol abuse, 51(5), 577-583. https://doi.org/10.1080/00952990.2025.2561982
MLA
Adinoff, Bryon, et al. "Challenging the 25-year-old 'mature brain' mythology: implications for the minimum legal age for non-medical cannabis use.." The American journal of drug and alcohol abuse, 2025. https://doi.org/10.1080/00952990.2025.2561982
RethinkTHC
RethinkTHC Research Database. "Challenging the 25-year-old 'mature brain' mythology: implic..." RTHC-05869. Retrieved from https://rethinkthc.com/research/adinoff-2025-challenging-the-25yearold-mature
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.