A teen who consumes alcohol is likely to have reduced brain tissue health, but a teen who uses marijuana is not, according to a new study.
Researchers scanned the brains of 92 adolescents, ages 16 to 20, before and after an 18-month period. During that year and a half, half of the teens — who already had extensive alcohol and marijuana-use histories — continued to use marijuana and alcohol in varying amounts. The other half abstained or kept consumption minimal, as they had throughout adolescence.
The before-and-after brain scans of the teens consuming five or more drinks at least twice a week showed reduced white matter brain tissue, study co-author Susan Tapert, neuroscientist at UC San Diego, told HuffPost. This may mean declines in memory, attention, and decision-making into later adolescence and adulthood, she said.
The teens who used the most marijuana did not show a change in brain tissue health, according to the study. The researchers did not test performance; they only looked at brain scans.
The study was conducted by researchers at UC San Diego and the University of Pittsburgh Medical Center and is scheduled to be published in the April issue of the journal Alcoholism: Clinical & Experimental Research.
The damage occurs because white matter brain tissue develops throughout adolescence and into a person’s 20s, Joanna Jacobus, postdoctoral fellow at the University of California, San Diego, and co-author of the study, told HuffPost.
Part of that still-developing brain tissue is where decision-making ability comes from, which can exacerbate substance use. “It becomes a cycle. If teens decrease their tissue health and cognitive ability to inhibit themselves, they might become more likely to engage in risky behavior like excessive substance use,” Jacobus said.