The association between the frequency of cannabis use among adolescents and the brain structure in adults
Une nouvelle survey published this month in the journal Drug and Alcohol Dependence revive the debate about cannabis use and brain development in adolescents. Consuming cannabis in adolescence would not have an impact on brain structure in adulthood. Few studies have tested the hypothesis that adolescent cannabis users exhibit structural alterations of the brain in adulthood. The present study tested associations between adolescent cannabis use patterns and brain structure in a sample of boys followed to adulthood, assessed prospectively.
Researchers from theArizona State University followed the cannabis use of about 200 boys in Pittsburgh in the late 1980 years, and then compared these consumption rates to high resolution MRI brain scans of the same 20 subjects years later.
"We found no difference in brain structure in adults" among those who reported high cannabis use in their youth, those who reported occasional occasional use, and those who said they did not use cannabis. , wrote the researchers. "Even boys with the highest level of exposure to cannabis in adolescence had subcortical brain volumes and cortical volumes at adult thickness similar to those boys with virtually no exposure to cannabis. during their adolescence. "
The science surrounding adolescent cannabis use and brain development is complex, politically complex and largely unresolved. The ASU study adds a new layer of data to the question but it is unlikely that concerns about the use of minors will be definitively resolved.
The study team was led by Madeline Meier, director of the laboratory on la addiction, health and USU behaviors . Meier and his colleagues acknowledged that their sample was relatively small, limited to young men in Pittsburgh who had driving problems in their youth and who relied on reported cannabis use. In addition, MRI imaging was performed only once per subject when they were about 30 years old.
"It's important to note that several studies previous revealed differences in brain structure among adolescent cannabis users or young adults with cumulative levels of cannabis exposure, "wrote Meier and colleagues. "These studies failed to determine whether differences in brain structure between these subjects persisted into adulthood. Our study suggests that this may not be the case. "
In other words, differences in cerebral structure may appear in cannabis precursors in their twenties but disappear when they reach their thirties.
Different measures of brain formation
Meier also recognized that the included MRI data, which measured subcortical brain volumes as well as cerebral cortical volumes and thickness, may not be the most accurate measures of cannabis-related cerebral dysmorphia. . In some previous studies, researchers have used other measures (form and density of gray matter, white matter integrity) to assess structural brain differences between young cannabis users and non-users.
The ASU study has a number of implications. Patterns of cannabis use among adolescents, whether light or heavy, "do not appear to have lasting effects on brain structure," the authors wrote. In this study, they "found no association between prospectively evaluated cannabis use in adolescents, subcortical brain volume and cortical brain volume and thickness in adulthood". .
The researchers warned that their study should be interpreted in context previous studies which allowed to examine the possible disturbances of the critical development of the brain, the hippocampal volume and the structure of the adult brain. "A review of these studies found that although some studies have found evidence of an association between the early age of cannabis use and adult brain structure, most studies have not done so. . "