Mike started drinking at age 14. At his very first party, he recalls, “I probably had 10 beers.” He partied for seven years while playing high school and college football, and the consequences of his drinking resemble a “Just Say No” campaign: blackouts, arrests, academic problems, emergency room visits, driving suspensions and mandatory treatment programs.

About 10 percent of eighth graders, 18 percent of 10th graders and 24 percent of high school seniors binge on alcohol. That is, they consume four drinks or more at a sitting if they are female or five or more if they are male at least once every two weeks. (For the same alcohol dose, women tend to have higher blood alcohol levels than men because of their smaller size, lower body water content and lesser ability to metabolize alcohol.) In addition, 44 percent of college students drink this much or more at least twice a month.

As Mike's case illustrates, binge drinking can lead to serious health and behavioral problems. Periodic heavy drinking is more damaging to both body and brain than smaller amounts of alcohol consumed more often because extremely high blood alcohol levels are toxic to organs, severely impair sensory and cognitive functions, and encourage habit formation or addiction.

Scientists have also identified a subtler, longer-lasting effect of heavy alcohol consumption among teenagers and young adults: deficits in learning and memory. An emerging body of data indicates that alcohol damages specific regions of the maturing brain. In addition, a youthful brain has weaker controls that would stop a person from drinking too much. Scientists are finding clues in the brain that may help them identify the most vulnerable young people—in hopes of halting problem drinking before it starts. According to psychiatry researcher Reagan R. Wetherill of the University of Pennsylvania, the aim is to bolster brain development “just enough” so that young people can “inhibit their own drinking behaviors before they act.”

Impulsive Minds

The teenage brain is a work in progress. In the past decade neuroscientists have revealed that the prefrontal cortex, which sits at the surface of the brain just behind the forehead, is relatively slow to reach maturity. This region is the seat of inhibitory control—the ability to stop oneself from acting impulsively—and of working memory, the mental scratch pad that enables a person to temporarily hold and manipulate information. Because the prefrontal cortex can mature years later than areas governing emotion and reward, teens explore and seek independence “before their inhibitory systems are in place,” disposing them toward risky behaviors, says psychiatry researcher Susan F. Tapert of the University of California, San Diego.

Youths whose brain maturation is slower than usual may be in particular jeopardy. In a study published in 2011 a team led by Tapert and her then graduate student Andria L. Norman, now at Wayne State University, tested the inhibitory control skills of 38 12- to 14-year-olds while they were in an MRI machine. They then tracked the youths for four years to see who would start using alcohol. The 21 kids who had begun heavy drinking had, in their original scan, shown less activation in 12 brain regions—including parts of the prefrontal cortex and the adjacent parietal cortex, which helps to produce planned movements—than the 17 who abstained. In teens who went on to binge, Tapert says, “the circuitry responsible for inhibiting an action is not operating quite perfectly.”

Wetherill has since tracked this diminished inhibitory capacity to a more specific brain location. In a study published in 2012 she and her colleagues used functional MRI to examine the brains of 20 12- to 14-year-olds who had never used alcohol but who came from families with alcohol problems. Teens from such families are more likely to start using and eventually abusing substances and in general tend to be more impulsive and defiant. Compared with 20 teens from families with no history of substance abuse, the brains of those in drinking families showed fewer and weaker connections between the frontal and parietal brain regions involved in planning, decision making and inhibitory control.

Studies published in 2014 and 2015 have confirmed that teens who go on to drink heavily—especially those with family histories of alcohol problems—have regions of slower brain maturation that may help identify at-risk teens before they transition into heavy drinking.

Thinking Too Hard

Not only are teenagers susceptible to the temptation of alcohol, but evidence suggests that drinking may harm their brains. The effects of drinking on the brain are not always straightforward. Yet clear differences in brain performance distinguish teetotalers from heavy imbibers. During the past decade pharmacology researcher Fulton Crews of the University of North Carolina at Chapel Hill School of Medicine and others have shown that a high blood alcohol level in rats, a model for human binge drinking, kills cells in the brain's frontal lobes and hippocampus, a hub for memory formation. Alcohol also suppresses the birth of new neurons, among other adverse effects. Adolescent rats are more sensitive than adult ones to both these consequences—meaning the damage is greater at smaller doses. Indeed, the blackouts, and resulting amnesia, that occur in about half of all college students after binge drinking may result from hippocampal damage, says Aaron M. White of the National Institute on Alcohol Abuse and Alcoholism.

Some of the earliest insights into how drinking might affect an adolescent's learning and memory emerged in a study published in 2010 in Tapert's laboratory. Her then graduate student, Alecia Dager, now a psychiatry researcher at Yale University, tested verbal working memory—the ability to retain verbal information for short periods—in 24 nondrinking and heavy-drinking teens. Dager and her team gave the young people lists of words and word pairs to study while recording their brain activity. Later they tested the teens' recall of the words. The drinkers remembered 78 percent of the words, compared with 85 percent in the nondrinkers. Activity was significantly higher in parts of the prefrontal and parietal cortex of the drinkers during both learning and testing phases, probably reflecting increased effort, Dager says. In contrast, the hippocampus in the drinkers was underactive, which, in this case, the scientists interpret as echoing their poorer recall.

In 2011 a team led by Lindsay M. Squeglia, now at the Medical University of South Carolina, reported parallel findings on spatial working memory. This cognitive capacity allows you to create mental maps for, say, finding your way to a friend's house or redrawing a figure from memory. While in a brain scanner, 55 nondrinkers and 40 heavy drinkers aged 16 to 19 tried to recall shapes they had seen, among other spatial working-memory tasks. The teens who had been drinking heavily for a year or two could do the exercises as well as the abstinent youths, although their parietal cortex was much more active. Teens who had been imbibing heavily for three or four years, however, performed worse on the tasks; activity in other brain regions—those involved in vision and motor control—declined. When kids start drinking, the brain works harder to keep up, Squeglia suggests, but over time it can no longer compensate, and performance drops.

In a study published in 2012 Tapert and her colleagues similarly showed markedly higher brain activity in heavy-drinking 15- to 19-year-olds compared with nondrinkers on tasks involving visual working memory, the ability to focus on what is important in the environment. The longer a teen had been drinking, the harder the brain toiled, whereas in the nondrinkers the regions expended less energy as the teen matured.

Then Tapert's team documented in the same youths both the characteristic brain signature of low self-control and later, after they became drinkers, signs of less efficient information processing. In late 2012 the team reported scanning the brains of 40 youths twice, three years apart, starting when the kids were 15 years old, on average, while they did visual working-memory tasks. In the 20 teens who became heavy drinkers between the scans, certain parts of the frontal and parietal cortex had been initially underactive, suggesting a lack of inhibitory control. Three years later, after they started to drink, other parts of these regions showed higher activity than they did in the 20 nondrinkers, a sign that the drinkers' brains had to exert unusual effort to perform the tasks. Studies by Tapert's lab, published in 2014 and 2015, show that differences in brain structure and function predate most heavy drinking in teens, and then the drinking itself causes further changes.

Collectively, the Tapert group's work suggests that the 24 percent of high school seniors and 44 percent of college students who regularly binge on alcohol might be handicapping their cognitive abilities. They score an average of 7 to 10 percent lower on verbal, visual and spatial tests than their classmates who drink very little or not at all. These young people may have more trouble reading a map, following verbal directions to a place, assembling a bookshelf, planning a project, staying organized and learning new vocabulary, among other cognitive challenges. Enough long-term data now exist on brain impairments and altered brain development, Squeglia wrote in 2015 in the American Journal of Psychiatry, to provide “a call for caution regarding heavy alcohol use” by teens, even before researchers have learned precisely how the damage occurs.

Someday it might be possible to “immunize” kids against the propensity to drink by bolstering their system for restraint in childhood. Wetherill is developing computer-based games and exercises that could strengthen inhibitory pathways and eventually boost self-control in the types of situations that teenagers typically face. The earlier prevention programs begin, the better. “A kid who starts drinking at 14 is four times more likely to become dependent on alcohol than a kid who starts drinking at 21,” White says. Restricted teen driving permits, raising the legal drinking age to 21, and various face-to-face and Web-based interventions are making a dent in teen drinking, he adds.

No one yet knows whether the brain can fully recover from heavy drinking during its final years of development. In some of Tapert's subjects, cognitive deficits still remain after a decade. Mike eventually quit drinking, graduated from college and is now a successful account manager for a marketing company. He still experiences significant gaps, however, in his recollection of certain people and events in his past. He can only guess to what extent binge drinking and blackouts contributed because he also sustained numerous concussions playing football. The latest research, however, suggests that his partying could have contributed to a long-lasting erosion of his memory.