The new research, published in the Archives of General Psychiatry, found that almost four out of five teens had tried alcohol and more than 15 percent were abusing it by the time they turned 18 years old. Some 16 percent were abusing drugs by age 18.

In comparison, 18 percent of adults meet standards for "lifetime abuse" of alcohol, and 11 percent meet the criteria for drug abuse, the study notes, suggesting an early start for at least some of those substance abusers.

"It's in adolescence that the onset of substance abuse disorders occurs for most individuals," said lead study author Joel Swendsen, director of research at the National Center of Scientific Research in Bordeaux, France. "That's where the roots take place."

"The reason we worry about it is that the earlier they use these substances the earlier they become addicted to it," said Susan Foster, vice president and director of policy research and analysis at the National Center on Addiction and Substance Abuse at Columbia University in New York.

Foster, who was not involved in the new study, said starting to use potentially addictive substances is especially dangerous to younger people because their brains are still developing.

"There's really a type of rewiring that goes on with continued use that can result in an increased interest in using and an inability to stop using," she said.

The new study is based on interviews with 10,123 U.S. teens between the ages of 13 and 18 years old, who were surveyed between February 2001 and January 2004.

Of the approximately 3,700 teens between the ages of 13 and 14, about 10 percent were drinking alcohol regularly -- defined as twelve drinks within a year. That number jumped to about half in the approximately 2,300 17- to 18-year-olds.

According to Swendsen's team, almost one in three of the regular users in the oldest age group met the criteria for lifetime alcohol abuse. And the median age of onset for alcohol abuse, with or without "dependence," was 14.

As for drugs, about 60 percent of the teens said they had the opportunity to use illicit drugs, such as marijuana, cocaine, tranquilizers, stimulants and painkillers.

About one in ten of the 13- and 14-year-olds said they used at least one such drug, and that increased to about 40 percent in the oldest age group. Pot was the most common type of drug used, followed by prescription drugs.

The median age of onset for drug abuse was 14 with dependence and 15 without dependence.

The researchers found differences between the kinds of youngsters who transitioned from general alcohol use to regular use, for example. Boys were more likely to transition between the usage groups, while blacks and other non-white ethnic groups were the least likely to do so.

"These findings may contradict common assumptions but are consistent with previous investigations in adult and adolescent samples," write the researchers.

Foster, whose organization published a comprehensive report on substance abuse in U.S. adolescents last year, also said these numbers are consistent with past research.

"We've had spikes and declines of abuse across the population," she told Reuters Health.

Swendsen's team writes that strategies need to target adolescents to prevent drug and alcohol abuse, but need to take into account the different forces that influence it.

"We don't need to bombard them with information that's beyond their stage of development, but don't think a 13-year-old doesn't know what cannabis is," Swendsen told Reuters Health in a telephone interview.

"Like any other disease it's very complex," Foster said. "There are a lot of… factors that come together."

She added that findings like those in the new study are especially helpful for parents and healthcare professionals who need to know how important their roles are in both preventing use and getting teens help.

"I think a lot of people don't understand yet the nature of the problem," Foster said.

SOURCE: bit.ly/HFkjYk Archives of General Psychiatry, online April 2, 2012.

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