A recent study finds no difference in brain images of adults who used cannabis as teens and those who did not.
Many physicians and policymakers base decisions about cannabis access for minors on the belief that teen brains are particularly vulnerable and can be susceptible to negative lasting impacts. In a new study, a group of researchers set out to test the hypothesis that teen cannabis users experience alterations to their brain structure into adulthood.
According to the study’s authors, comprised of researchers from Arizona State University and the University of Pittsburgh, most scientific research attempting to track the impact of cannabis on the growing brain is done by using retrospective reports from adults.
The new groundbreaking longitudinal study used data from the Pittsburgh Youth Study, a sample of boys ages 13-19 who annually self-reported cannabis use. Then the research team followed up with a sample of the boys, now adults ages 30-36, who underwent structural neuroimaging.
The results showed no recognizable differences in the brain structure of the boys who used marijuana compared to the boys who did not.
“Adolescent cannabis use is not associated with structural brain differences in adulthood,” the authors concluded.
The researchers gained their results by placing the sample of youth respondents into four cannabis trajectories, or four categories:
- Non-users or infrequent users
- Users who stopped
- Chronic users
According to the study’s authors, there was no difference in brain structure among the members of the four cannabis categories.
They concluded: “Boys in different trajectory subgroups did not differ on adult brain structure in any subcortical or cortical region of interest.”
Those regions play a role in reasoning, emotional, and social functions by the brain.
The study, “Associations between adolescent cannabis use frequency and adult brain structure: A prospective study of boys followed to adulthood,” was published online in July in the journal Drug and Alcohol Dependence. The study can be found here.
Teen Cannabis Use and the Growing Brain
The study’s findings add to a growing body of evidence disputing the popular belief that cannabis use is associated with changes in brain structure. Two other recent studies also found that cannabis use amongst teens has no widespread impact on brain structure.
The first study, published in the journal Neuropsychopharmacology, compared 781 brain scans of non-marijuana users, occasional users (one to two times weekly), and frequent users (more than three times weekly). The test subjects ages spanned from 14 to 22 years old.
By using neuroimaging, researchers found that the brains of those young people who did not use marijuana showed no remarkable differences to those who occasionally or frequently used marijuana.
In a study published in the journal Psychiatry Research, researchers looked at the brains of long-term marijuana users. What they found indicated consistent marijuana for over two decades did not have a widespread impact on the thickness of the brain, nor did it have a significant impact on cognitive performance.
It’s been widely misconceived that marijuana is a “gateway drug” that adversely alters teenagers’ behavior. A recent study published in the journal Addiction revisited that theory. Researchers examined a survey of teens over a five-year period focusing on whether cannabis use led to conduct problems, like stealing, lying, skipping school, arson, or using dangerous drugs.
The results showed no evidence that teen marijuana use encouraged future bad behavior, or was a precursor to using dangerous drugs later on in life.
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