Researchers at the University of California San Diego have discovered that teenagers who begin using cannabis exhibit slower improvements in memory, attention, and cognitive abilities over time in comparison to those who do not use it.
This extensive study looked into brain development over a long-term period among U.S. teens and highlighted concerns regarding cannabis use, which is thought to involve around 18 million Americans.
Highlights
- A recent study explored the link between early use of cannabis and cognitive growth.
- The research followed over 11,000 adolescents ranging from ages 9-10 to 16-17, utilizing self-reports alongside toxicological samples.
- Participants undertook various tasks to evaluate their memory, attention, processing speed, and language abilities.
The study tracked 11,036 individuals from the ages of 9 to 10 through to 16 and 17, focusing on their cognitive abilities and substance use patterns.
Data collection included self-reports and toxicological analyses—like hair and urine tests—that can identify substance use over different time frames.
“Hair samples can detect usage for about three months on average and are especially effective in identifying consistent users in adolescents,” the study explained.
Participants engaged in tests assessing their memory, language, visuospatial skills, and processing speed, which includes completing puzzles and interpreting maps.
Those who consumed cannabis displayed less growth in these cognitive areas over time compared to their non-using peers, despite starting out on similar or slightly higher levels when younger.
As these teens aged and began using cannabis, their cognitive progression slowed or plateaued, while their peers who didn’t use cannabis kept improving. This study was published on April 20 in the journal Neuropsychopharmacology.
Experts identified THC, the primary psychoactive component in marijuana responsible for its effects, as a significant influence on cognitive development.
THC specifically correlated with diminished gains in episodic memory, which involves recalling past experiences and emotions. Conversely, a small group of teens, only exposed to CBD (a non-psychoactive compound in cannabis), did not exhibit the same decline.
“These findings suggest THC is likely influencing the observed cognitive changes,” noted Natasha Wade, an assistant professor at UC San Diego and the lead author of the study.
“It underscores the complexity of cannabis products since some labeled as CBD may still contain THC,” Wade added.
Although the differences seen in cognitive abilities were modest, researchers stress their importance. Adolescence is a crucial period for brain development, and even slight changes can affect daily functioning.
“This is a critical time for brain growth, and the data shows that teens starting cannabis use are not improving like their non-using peers,” Wade commented.
“These minor differences may accumulate significantly affecting learning and memory in practical situations.”
THC was recognized as the key element associated with negative impacts on cognitive development.
To mitigate these consequences, researchers recommend delaying cannabis use since many individuals cannot ensure they are avoiding THC entirely.
“The results support efforts to postpone the initiation of cannabis use in early adolescence and to incorporate education on cognitive development during these sensitive years,” the study concluded.
Responses to the findings varied, with some individuals reflecting on their past cannabis usage with regret, others expressing surprise at the implications related to young users, and some advocating for comparisons with alcohol and tobacco.
The legal status of cannabis in the U.S. has evolved significantly, with 29 states allowing recreational and medicinal use, while four states maintain a complete ban. Other states have mixed regulations, often limited to CBD or medicinal uses.
“As cannabis becomes more accessible, it’s essential for both families and teens to grasp its potential effects on developing brains,” Wade emphasized. The teenage brain is still developing until around the age of 25.
In 2022, statistics revealed that 30.7% of high school seniors reported cannabis use in the previous year, with 6.3% admitting to daily use.
The CDC notes that teens who use cannabis are more prone to dropout compared to their non-using counterparts.
Individual experiences with cannabis can vary, influenced by factors like THC concentration, frequency of use, and genetic predispositions.
The University of California research team considered a range of influences, including family environment, mental health, other substance use, and preliminary cognitive performance as they analyzed the data.
The researchers emphasized the necessity of following this cohort into young adulthood to fully comprehend the links between THC exposure and brain development. They highlighted the impact of the timing of cannabis initiation.
