A long-term study involving more than 11,000 children and adolescents showed that recreational cannabis use is associated with a slight slowing of the development of memory, attention, and thinking skills.
These findings reinforce public health recommendations that teenagers should avoid cannabis use, due to its potential impact on the developing brain.
The study, the largest of its kind in the United States, was based on data from the Adolescent Cognitive Brain Development Study, which followed more than 11,000 participants aged 9 or 10 to 16 or 17.
During the follow-up period, participants underwent annual biological tests, including blood, urine, breath, and saliva samples, along with questionnaires about their use of cannabis and other substances. Use was mostly recreational, with a small percentage using cannabidiol (CBD) for medical purposes under medical supervision or with parental consent.
The researchers assessed the cognitive development of the participants through tests that measured memory, processing speed, attention, language, visuospatial abilities, and behavioral control.
The results showed that adolescents who began using cannabis experienced a slower development of these skills compared to their peers. It was observed that they were performing at a similar or better level before starting to use it, but their rate of progress slowed afterward.
Although the study does not prove a direct causal relationship, it took into account multiple factors such as family background, mental health and use of other substances, which strengthens the results.
The analysis also showed that the effect was most pronounced in adolescents exposed to tetrahydrocannabinol (THC), the main psychoactive component in cannabis, while no similar effects were clearly observed in those whose use was limited to cannabidiol (CBD).
Lead researcher Natasha Wade points out that "adolescence is a sensitive stage for brain development, and adolescents who begin using cannabis do not achieve the same pace of cognitive development as their peers."
She adds that these differences may seem minor at first, but they can accumulate over time to affect learning, memory, and daily performance.
The researchers also noted that even slight differences in cognitive abilities can be reflected in academic achievement, standardized tests, and higher education opportunities, and may extend to life skills such as leadership.
Researchers emphasize the importance of families and adolescents being aware of the potential effects of cannabis during this sensitive stage of life.
The study was published in the Journal of Neuropsychopharmacology.
