Overview
- Published Monday in Neuropsychopharmacology, the peer‑reviewed analysis followed more than 11,000 ABCD participants from ages 9–10 to 16–17 and will continue into young adulthood.
- Teens who began using cannabis showed smaller gains over time in memory, attention, language, and processing speed compared with peers who did not use.
- In many cases early scores were similar, but progress flattened after cannabis use started while classmates kept improving.
- Biological tests alongside surveys detected exposure, and THC evidence tracked with worsening memory over time, while CBD did not show that pattern.
- The authors controlled for prior cognition, family background, mental health, and other substance use, and they cautioned the results do not prove direct causation.