Heavy alcohol use in adolescence is linked to disruptions in white-matter integrity, new research suggests.
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In a case-control study of more than 400 participants, the association was more pronounced in younger adolescents and in the anterior and middle corpus callosum, which serve the interhemispheric integration of frontal networking and communication.
The results provide clinicians with yet another reason to ask adolescents about their alcohol use, said investigator Adolf Pfefferbaum, MD, Center for Health Sciences, SRI International, Menlo Park, Calif., and professor emeritus at Stanford (Calif.) University.
However, when questioning adolescents about their alcohol use, “sometimes it’s better to ask: ‘How much alcohol do you drink?’ ” instead of just asking if they drink, Dr. Pfefferbaum said in an interview. That’s because they may be more willing to answer the first question honestly.
It’s also important for clinicians to nonjudgmentally tell teens there is evidence “that heavy drinking is bad for their brain,” he added.
The findings were published online Dec. 30, 2020, in JAMA Psychiatry.
Fractional anisotropy
Adolescence is a critical period of physiological and social maturation accompanied by significant structural, functional, and neurochemical brain changes, the investigators noted.
Diffusion tensor imaging (DTI) produces a measure called fractional anisotropy (FA), which characterizes some of these brain changes by measuring molecular water diffusion in the brain.
“FA is a measure of the integrity of brain white matter; so, the part of the brain that connects neurons with each other,” Dr. Pfefferbaum said. He added that FA decreases in diseases such as multiple sclerosis (MS), reflecting “some kind of pathology.”
Affected fiber systems include the corpus callosum, superior longitudinal fasciculus, internal and external capsule, brain stem, and cortical projection fibers. Disruption of these neural systems may degrade neural signal transmission and affect certain cognitive functions, possibly resulting in enhanced impulsivity, poor inhibitory control, and restricted working memory capacity, the researchers wrote.
FA follows an inverted U-shaped pattern. “The natural trajectory is to increase from infancy up to middle adolescence and then, as we get older, from about age 25 to 30 years, starts to go down. Our brains are starting to show signs of aging a bit by then,” said Dr. Pfefferbaum.
The current analysis assessed 451 adolescents (228 boys and 223 girls) from the NCANDA study, for whom researchers had four years of longitudinal DTI data. All were aged 12- 21 years at baseline.
The NCANDA cohort was recruited across five U.S. sites. Participants are assessed yearly on psychobiologic measures, including brain maturation. The cohort, which did not have any significant substance abuse upon entry, is balanced in terms of gender and ethnicity.
The investigators quantified the developmental change of white-matter (WM) integrity within each individual as the slope of FA over visits. They also examined altered developmental trajectories associated with drinking onset during adolescence and the differential alcohol associations by age with specific regional WM fiber tracts.
Researchers assessed drinking on a scale of 1-4, based on the youth-adjusted Cahalan score. The scale considers quantity and frequency to classify drinking levels based on past-year self-reported patterns.
Altered trajectory
Results showed that 291 participants (37.2%) remained at no to low drinking levels (youth-adjusted Cahalan score, 0) throughout the time points examined, and 160 (20.5%) were classified as heavy drinkers for at least two consecutive visits (youth-adjusted Cahalan score >1).