Brown Studies Consequences of Adolescent Alcohol Use
Long-term studies on adolescent alcohol use are revealing the effects of alcohol exposure on brain development and the genetic and environmental factors for increased risk of adolescent alcohol use, said Dr. Sandra Brown at NIAAA’s 12th annual Jack Mendelson Honorary Lecture held via videoconference recently.
“For over 15 years now, we’ve had evidence that the brains of youth exhibit neuroanatomical differences across ages from childhood to adolescence to young adulthood,” said Brown, vice chancellor for research and distinguished professor of psychology and psychiatry at the University of California, San Diego.
Adolescence—the transitional period that begins at puberty and continues to legal adulthood—is a pivotal time for children. During this period, they become more independent, develop social skills and learn to control their own behaviors, thoughts and emotions. They also take more risks, such as using alcohol and other substances.
The behavior of adolescents has changed over the past 25 years, said Brown. Today, almost all youth have smartphones and fewer get driver’s licenses. The teen pregnancy rate has decreased, while the rate of depression and anxiety in teens is increasing.
Alcohol is an adolescent’s preferred substance of use, she said. The rate of use increases dramatically from 8th to 12th grade. Eight percent of eighth graders reported drinking in the last month, in a national survey of substance use. By 12th grade, 30 percent have consumed alcohol in the last month and 20 percent reported being drunk in that period.
Youth drink differently than adults, Brown continued. Those under 21 drink about half as often as adults, but when they do drink, they consume twice as much. Because alcohol is illegal for underage drinkers, they often drink faster.
There are consequences of teen drinking. A third of teens who drink say their grades suffered and one-fifth reported unsafe driving related to alcohol use. One in 2 say they regret their behavior while under the influence and 1 in 5 admit that alcohol created relationship problems, including early, unwanted or risky sex.
Animal models of adolescent alcohol consumption and its consequences have found that juvenile mice consume 2 to 3 times more alcohol than adults, Brown explained. They are more sensitive to the rewarding effects of alcohol, and have memory and executive function problems because of it.
To determine how early these neurological problems and mood disruptions begin after an adolescent starts drinking, researchers set up a long-term study to observe the effects in boys and girls ages 12-14. Three years after the study started, they found that learning and memory problems followed the onset of heavy drinking. Not all of these problems are permanent, however.
Brown found that when youth stop drinking heavily, they spend more time on homework and increase their exercise. Following abstinence, boys are more anxious than girls initially, while girls showed poorer mood states for longer, her team found. It’s not clear why.
In 2012, NIAAA established the National Consortium on Alcohol and Neurodevelopment in Adolescence (NCANDA). Brown, who co-directs the consortium with Dr. Susan Tapert, said 5 sites across the U.S. enrolled more than 830 adolescents.
Each year, study participants undergo brain imaging scans, neuropsychological testing and assessments of their behavioral functioning, including alcohol use and related problems. The group’s goal is to determine the effects of alcohol use on the developing adolescent brain and examine brain characteristics that predict alcohol use problems.
“Over the course of 10 years of study, we will be observing these youth during key periods of time when it’s most likely they will have onset and offset of alcohol disorders,” Brown said.
So far, the consortium researchers have found that heavy drinking during adolescence disrupts normal brain growth trajectories in inhibition and integration. They’ve also discovered that youth drinkers have more sleep disturbances, suggesting that alcohol and sleep influence each other.
“Impulsivity appears to be a strong predictor of earlier consumption rather than later consumption,” Brown reported. These findings suggest that risk factors change as a person matures.
Stress and trauma appear to be related to the onset of moderate to heavy alcohol use. In the NCANDA sample, almost 50 percent have experienced a traumatic event such as a death in the family, a natural disaster, severe accident or sexual assault or abuse.
Brown said the consortium has also developed a smartphone app called M-NCANDA to assess what youth are doing daily.
Although NCANDA is a large study, “It takes much more than that, especially if we’re interested in looking at additional roles of genetics and other environmental factors,” cautioned Brown.
Another study, the Adolescent Brain Cognitive Development (ABCD) Study that Brown co-directs with Dr. Terry Jernigan, has recruited almost 12,000 9- and 10-year-olds and will follow them for a decade. The objectives of the study are to develop standards for normal brain development and measure individual developmental trajectories of cognitive function and health behaviors.
The larger sample size will enable researchers from the 21 sites across the country, as well as scientists around the world, to study the roles of genetic and environmental factors on development and how physical activity, sleep and social activities influence development. Through ABCD, scientists will also be able to observe how the onset of mental health disorders might interact with substance use.
“NCANDA and ABCD are not experimental studies, they are observational studies,” Brown concluded. “Their data should lead to hypothesis-driven experiments that can answer important developmental questions.”
The Mendelson Lecture honors Dr. Jack Mendelson’s scientific contributions to the field of alcohol research. It features an investigator who has made significant contributions to understanding susceptibility to alcohol use disorder (AUD), alcohol’s effects on the brain and other organs and the prevention and treatment of AUD.