Cannabis and the Developing Brain: Why Waiting Until After Age 25 Matters

                

Many people are surprised to learn that the brain continues to develop until approximately age 25. During the teen and young adult years, the brain is strengthening important connections that support:

  • Learning and memory
  • Attention and concentration
  • Decision-making
  • Emotional regulation
  • Problem-solving
  • Planning and impulse control

Cannabis, particularly THC (tetrahydrocannabinol), can interfere with these developing brain systems. Because the brain is still maturing, young people may be more sensitive to the effects of cannabis than older adults.

Cannabis and mental health

Not everyone who uses cannabis will experience mental health problems. However, research shows that cannabis use during adolescence and young adulthood may increase the risk of certain mental health challenges, particularly among people who use cannabis frequently, start at a young age, have a family history of mental illness, or use high-THC products.

Cannabis use has been associated with:

  • Depression
  • Anxiety
  • Social anxiety
  • Suicidal thoughts and behaviours
  • Psychosis
  • Schizophrenia-spectrum disorders

Understanding psychosis

Psychosis is a condition that affects how a person understands what is real. Symptoms may include:

  • Seeing or hearing things that are not there
  • Strong beliefs that are not based in reality
  • Difficulty organizing thoughts
  • Increased suspicion or paranoia

While psychosis is uncommon, research shows that cannabis use can trigger temporary psychotic symptoms in some individuals and may contribute to the development of longer-lasting psychotic disorders in people who are vulnerable. The risk appears to be greater with frequent use, earlier age of initiation, and higher-THC products.

Who may be at greater risk?

Some young people may be at higher risk to the effects of cannabis than others, including those who:

  • Begin using cannabis at an early age
  • Use cannabis frequently or daily
  • Use products with high THC content
  • Have a personal or family history of mental illness
  • Use cannabis alongside alcohol or other substances

Sources

  • Centers for Disease Control and Prevention (CDC). Cannabis and Teens (2024). [cdc.gov]
  • Centers for Disease Control and Prevention (CDC). Cannabis and Brain Health (2024). [cdc.gov], [assets.ctfassets.net]
  • Wade N., et al. Longitudinal neurocognitive trajectories in adolescents following cannabis use onset. Neuropsychopharmacology (2026). Summary available through UC San Diego and University of California. [today.ucsd.edu], [universityofcalifornia.edu]
  • Young-Wolff K., et al. Adolescent Cannabis Use and Risk of Psychotic, Bipolar, Depressive, and Anxiety Disorders. JAMA Health Forum. 2026. [pubmed.ncbi.nlm.nih.gov]
  • Hall W., et al. Relationships between cannabis use and mental disorders: assessing the coherence of evidence from studies with different methodologies. The Lancet Psychiatry. 2026. [thelancet.com]
  • Johns Hopkins Medicine. Understanding How Cannabis Use Affects Brain Development and Mental Health (2024). [hopkinsmedicine.org]
  • Johns Hopkins Bloomberg School of Public Health. Cannabis Use Disorder Among Young People Linked to Diagnosis of Psychiatric Disorders (2026). [publichealth.jhu.edu]
  • Kapler S., et al. Assessing evidence supporting cannabis harm reduction practices for adolescents at clinical high-risk for psychosis. Psychological Medicine. 2024. [cambridge.org]