Consuming a little marijuana recreationally only once or twice can change a teenager's brain, according to a study of 14-year-old Europeans who found differences in brain volume between those who tried it and those who did not.
The study is the first to present evidence that an increase in gray matter in certain parts of the adolescent brain is a "likely consequence" of low-level marijuana use, according to its authors. , researchers at the University of Vermont in the United States.
The research was conducted at the age of 14, from Ireland, England, France and Germany as part of a long-term European project known as "Image."
Among the participants were 46 adolescents who reported having used marijuana once or twice in their lives and whose brains showed a higher volume of gray matter in regions rich in cannabinoid receptors.
The largest gray matter differences between those who used marijuana and those who were not detected in the brain amygdala, involved in processes related to emotions, and in the hippocampus, linked to the development of memory and spatial abilities.
Differences between the two brains persisted despite the control of many variables, including sex, socioeconomic status, and alcohol and nicotine use.
"Consumption of just one or two joints appears to alter gray matter volumes in these adolescents," said Hugh Garavan, lead author of the study and professor of psychiatry at the University of Vermont.
What is meant by increased gray matter volume in certain parts of the adolescent brain is still unclear, and more research is needed to determine if the results of this study apply to more diverse populations.