According to the 2002 National Survey on Drug Use and Health, 36 percent of teenagers with a D grade average reported that they used cigarettes, alcohol, or illegal drugs in the past month. Use declined steadily with improved academic performance:

• 20 percent of students with a C average
• 13 percent of students with a B average
• 6 percent of students with an A average

The connection between poor academic performance and substance abuse probably involves a number of factors, says Mike Alle, supervisor of Intake Services at Hazelden Center for Youth and Families in Plymouth, Minn. Among them are missed classes, lower test scores, and memory problems.

"If you've been studying hard over a long period of time before you start abusing alcohol or other drugs, you may do fairly well in school for a while," Alle says. "Long-term memory at the onset of substance abuse doesn't appear to be affected. However, substance abuse does affect short-term memory and can impact long-term memory, or the ability to retain new information. So, with sustained marijuana use, for instance, even long-term memory could be impaired, and a decrease in academic performance is only one of many symptoms of substance abuse."

Research on adolescent development gives this statement a new urgency. It's now clear that the human brain continues to develop throughout the second decade of life. Scientists describe the brain during these years as highly "plastic," meaning that connections between brain cells are constantly being rewired on the basis of new experiences.

Alcohol may interfere with this process, with effects that last for years. Sandra Brown and colleagues at the University of California, San Diego measured substance abuse and mental abilities in a group of students with an average age of 16. Researchers followed up with assessments over the next seven years, until most of the students turned 24. The results: Students with the highest levels of substance abuse as teenagers got the lowest scores on tests of memory and learning in their early 20s.

Patterns of drinking that involve repeated cycles of abuse and withdrawal appear to do the most damage. Yet this is exactly the form of drinking that teenagers are likely to do. "Adults can go to a liquor store, purchase a six-pack, take it home, have a beer, and then put the rest in the refrigerator," Alle says. "Adolescents don't do that. They don't just sit down and have one beer. They usually consume abusively--to intoxication."

At present, researchers aren't sure how much academic performance improves after students stop drinking and using other drugs. "There is indirect evidence in the form of improvements in scores on tests of attention and memory after teens stop using," says Aaron White, assistant research professor in the Department of Psychiatry at Duke University Medical Center. But for the heaviest users, White adds, deficits in brain development may be permanent.

As a parent, you can prevent students from losing academic ground to substance abuse. A report from the National Clearinghouse for Alcohol and Drug Information suggests that you:

• Talk with your teenager about the dangers. Numerous studies show that parental disapproval is a powerful deterrent to drinking and other drug use.
• Spend regular time with your teenager. Listen without judgment and try to understand the pressures that adolescents face. When your child makes wise choices, offer praise.
• Keep track of where your teenager is and meet his or her friends.
• Get teenagers involved in after-school activities so they won't be able to just "hang out" in the afternoon--the time when they are most likely to experiment.
• Be a positive role model. Don't abuse alcohol or drugs yourself.

--Published December 26, 2005