UCSD Study: Teen Cannabis Use Slows Memory, Thinking
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- Natasha Wade and colleagues at UC San Diego published a Neuropsychopharmacology study using data from 11,036 participants in the Adolescent Brain Cognitive Development (ABCD) Study, tracking children from ages 9–10 through 16–17.
- The cognitive findings showed teenage cannabis users initially performed as well as or slightly better than nonusers, but their gains in memory, attention, language, and processing speed leveled off while nonusers continued improving.
- THC exposure was linked to greater memory declines than nonuse, while the same pattern was not observed for CBD exposure — though the CBD group was smaller.
- The researchers measured cannabis use with hair, urine, and saliva toxicology alongside self-reports, capturing both recent use and exposure from months earlier.
- The analysis adjusted for family background, mental health, other substance use, and each participant's pre-use cognitive abilities, though the study does not establish direct causation.
- Wade recommended delaying cannabis use, noting that as cannabis becomes more widely available, families and teens should understand its potential effects on the developing brain.
Why it matters: As cannabis becomes more widely available, this 11,036-participant ABCD analysis — the largest long-term US youth brain-development study — points to THC specifically, not CBD, as the likely driver of slowed cognitive gains in users, with even modest differences potentially affecting classroom performance and learning during a critical period of brain development.
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