Does cannabis harm the adolescent brain?
Yes, the risk is markedly higher in adolescents. Studies show: regular use before age 18 correlates with reduced IQ (up to –8 points), worse school outcomes, higher psychosis risk and altered brain structure (prefrontal cortex).
Key facts
- IQ reduced up to –8 points
- Psychosis risk 2–4×
- Prefrontal cortex effect
- In adults: largely reversible
Detailed answer
The brain matures until ~25. Regular cannabis use before 18 acts during this sensitive phase on synaptic formation and myelination, especially in the prefrontal cortex (impulse control, decision-making). Longitudinal studies (Meier et al. Dunedin, Volkow): up to –8 IQ points, poorer grades, elevated psychosis risk (2–4× with genetic vulnerability), higher depression risk. Important: effects are stronger with daily and high-potency use. In adults, cognitive effects are largely reversible after weeks of abstinence.