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NEW YORK (Reuters Health) - Kids who drink or use drugs before the age of 15 are more likely than their peers to develop a range of problems by adulthood, including drug dependence, research suggests.
In a study that followed more than 1,000 New Zealanders for 30 years, researchers found that those who started experimenting with drugs or alcohol before they were 15 were at greater risk of drug or alcohol dependence, contracting a sexually transmitted disease or being convicted of a crime by adulthood.
Girls who reported early substance abuse were also at higher risk of becoming pregnant before the age of 21.
The findings, reported in the journal Psychological Science, add to evidence that early drinking and drug use can put kids on a path toward long-term problems.
The study found that early drinking was not only risky for teenagers with a history of bad behavior, or those from families with substance abuse problems, lead researcher Dr. Candice Odgers told Reuters Health.
That is, it doesn't matter if a teen is a "good kid" from a "good family," said Odgers, an assistant professor of psychology and social behavior at the University of California, Irvine.
Of course, not everyone who tries alcohol and drugs in the early teens is headed for trouble, the researcher noted.
However, she said, parents should know that early adolescence is a "critical period of development" and that the adolescent brain may be especially sensitive to the effects of alcohol and other drugs.
Odgers and her colleagues based their findings on data from a New Zealand health study that followed 1,037 participants for 30 years, starting from the age of 3. At the ages of 13 and 15, participants were asked whether they had ever tried alcohol or illegal drugs.
Overall, 11 percent of 13-year-olds said they had used alcohol or drugs multiple times. Half of these early starters, Odgers's team found, had no history of serious behavioral problems or family factors likely to put them at higher risk of substance abuse.
They were, however, at increased risk of significant problems in adulthood. Early starters were two to three times more likely than their peers to become drug- or alcohol-dependent, contract a sexually transmitted disease or have an early pregnancy. They were also about four times as likely to have had a criminal conviction.
"Parents are caught between the mixed messages that early substance exposure is harmful for their kids, versus it is okay for their young teen to experiment with alcohol and other drugs as the majority will not become addicts or ruin their lives," Odgers said.
This study, she added, "contains a couple of important messages for parents, namely that teen who use substances multiple times before their 15th birthday are at risk for a wide range of poor health outcomes."
Most parents, Odgers noted, do not think that their young teenager is using drugs or alcohol. However, she said, national surveys indicate that almost half of U.S. teens younger than 15 have used drugs or alcohol.
SOURCE: Psychological Science, October 2008.