(NEW YORK) -- Ninety percent of drug addictions begin in high school, according to a new study released Wednesday.
Researchers from the National Center on Addiction and Substance Abuse, or CASA, found that nine out of 10 American addicts started smoking, drinking or using drugs before the age of 18 and one in four of those people become addicted to some sort of drug.
"We now have enough science to show that adolescent substance use is America's number one public health problem," said Susan Foster, senior investigator of the study. "By recognizing this as a health problem and responding to it, we can actually make the difference by improving the life prospects of teens and saving costs in society."
Adolescence is a critical period of brain development and experts say the teen years put people at increased danger of addiction because their brains are more sensitive to substances and they're more likely to experiment and take risks.
"The brain is still developing up until age 25, so when you put nicotine and psychoactive substances in the body, it's actually messing with the brain as it's developing," said Dr. Stanton Glantz, director of the University of California at San Francisco Center for Tobacco and Research and Education. "Nicotine tends to be the gateway drug when kids start smoking younger. They're more likely to become addicted and smoke for a longer period of time."
Glantz continued to say that smoking creates permanent changes in the brain. When a person quits, some of those changes reverse, but never completely. Researchers also know that tobacco, alcohol and other drugs act similarly in the brain, so that the use of one substance heightens the risk of dependence on others.
"Addiction is the most costly health problem in America today, and it drives 70 other diseases that require hospitalization," said Foster. "It drives a host of very costly health and social problems that are largely preventable. We can do something about it."
Foster said preventing teen for substance use begins with screening young people for their mental health and family addiction history.
Society also needs to move away from a culture that glorifies and promotes substance use as a way to relax or have fun and improve accessibility of available treatment, she said.
Copyright 2011 ABC News Radio