The new report, released Tuesday, also warns that such teenagers are more likely to have several partners than teens who abstain from booze and drugs.
Joseph Califano, head of the National Center on Addiction and Substance Abuse at Columbia University, told CBS Radio News this report has a clear message for parents.
"If you find your teen is drinking or using drugs, you must talk to that child about sexual activity as well," he said.
The report is a result of a two-year study.
Teens who are 14 and younger and drink are twice as likely to have sex than those who don't in the same age group. The risk is doubled for 14-year-old teens using drugs, said the report from the Center on Addiction and Substance Abuse at Columbia University.
Older teens who drink are seven times as likely to have intercourse than non-drinking teens, and are twice as likely to have it with four or more partners. Drug-using older teens are five times as likely to have sex than nonusers, and three times as likely to have it with four or more partners.
"While it's clear that teens who drink and use drugs are likelier to have sexual intercourse at earlier ages and with many partners, it is not clear which starts first - sexual intercourse or drinking and drug abuse," said Califano.
The CASA findings are based on national data of more than 34,000 teen-agers.
Young people in general have more sex today than 30 years ago. In a study from 1970, less than 5 percent of the 15-year-old girls questioned had engaged in sex. In 1972 the number for boys the same age was 20 percent. In 1997, said the CASA analysis, 38 percent of the 15-year-old girls and 45 percent of the 15-year-old boys had had sex.
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