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It is well known that during adolescence the brain undergoes significant changes—marked by decreases in gray matter (neuronal cell bodies, dendrites, unmyelinated axons, and synapses) and increases in white matter (myelinated axons that coordinate signals between neurons). To examine the effects of alcohol consumption on neurodevelopment, Adolf Pfefferbaum, M.D., of SRI International and colleagues compared structural MRI data from 483 youth aged 12 to 21 before the initiation of drinking and at follow-up one and two years later. Youth were also asked about their alcohol and marijuana use at each follow-up.
“At baseline, all participants met the study-entry criteria for no or low drinking and drug use,” Pfefferbaum and colleagues wrote. (No/low drinkers reported drinking less than one time per month, less than two drinks on average, and less than four drinks maximum). “As anticipated, however, a proportion of these youths (n=127) initiated drinking to levels that exceeded, to varying degrees, the study entry criteria, thereby enabling pursuit of a naturalistic study on the effects of drinking on the adolescent brain.”
At the two-year follow-up, 356 youth continued to meet the study’s no/low drinking criteria and 127 youth transitioned from the no/low drinking group to one of two drinking groups: 65 moderate drinkers and 62 heavy drinkers (see online data supplement for descriptions of alcohol consumption in heavy and moderate drinkers).
The authors found that while no/low drinkers experienced reductions in gray matter and increases in white matter over time, “[v]olumes of frontal, cingulate, and total gray matter declined more rapidly and central white matter expanded more slowly in the heavy drinkers than in the no/low drinking group.”
In an accompanying editorial, Jennifer L. Stewart, Ph.D., of Queens College, City University of New York, pointed out: “It is important to note that baseline gray and white matter volume alone did not differentiate the alcohol use groups, which suggests that the differences in brain structure were not present before onset of heavy alcohol use. On the contrary, increases in alcohol consumption paralleled aberrant structural brain changes over the two-year period, providing evidence supporting the idea that gray and white matter derailment is indeed present at early stages of problem alcohol use.”
“What we’re seeing here is an alteration in normal development,” Pfefferbaum said in the April AJP audio podcast. “When we did this study, we saw that children as young as 12 sometimes start drinking.” Clinicians should be sure to ask youth about alcohol and other drug use, just as they do adults, he said.
(Image: Triff/Shutterstock)
