Study Scanned Brains of 92 Subjects, 16 to 20, For 18 Months
A teen who uses alcohol is likely to have reduced brain tissue — but a teen who uses marijuana is not, according to a 2012 study.
Scientists looked at the brains of 92 adolescents, ages 16 to 20, before and after an 18-month period, reports Kathleen Miles at the Huffington Post. Half of the teens — who already had histories of alcohol and marijuana use — continued to use both in varying amounts during that year and a half. The other half of the teens abstained or consumed very minimally, as they had during adolescence.
Before-and-after brain scans of the teens having five or more drinks at least twice a week showed reduced white matter brain tissue, according to study coauthor Susan Tapert, who is a neuroscientist at the University of California-San Diego. According to Tapert, this could result in memory declines, and could impact attention and decision-making into adulthood.The teens who used the most marijuana showed no change in brain tissue health, according to the study. Only brain scans, not performance, were studied.
The study, conducted by researchers at UC San Diego and the University of Pittsburgh Medical Center, was published in the scientific journal Alcoholism: Clinical & Experimental Research in April 2013.
White matter brain tissue is still developing throughout a person’s adolescence and into their 20s, and that is why the damage occurs, according to Joanna Jacobus, a post dodctoral fellow at UC San Diego and coauthor of the study.
Part of the damaged brain tissue is that which controls decision-making ability, which can result in further substance use, she said.
“It becomes a cycle,” Jacobus said. “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.”
The researchers said they weren’t sure why alcohol produced damage and cannabis did not. They said the study results cannot be considered definitive without more research. It isn’t known if the reduced brain tissue health found with adolescent alcohol use is permanent.
Each teen in the study received brain imaging, a substance-use assessment, and toxicology screening at the beginning and at the end of the study, as well as substance-use interviews every six months.