Teens who start having sex significantly earlier than their peers also show higher rates of delinquency in later years, new research shows.

A national study of more than 7,000 youth found that adolescents who had sex early showed a 20 percent increase in delinquent acts one year later compared to those whose first sexual experience occurred at the average age for their school.

In contrast, those teens who waited longer than average to have sex had delinquency rates 50 percent lower a year later compared to average teens. And those trends continued up to six years.

“We're not finding that sex itself leads to delinquency, but instead, that beginning sexual relationships long before your friends is cause for concern,”   said Stacy Armour, co-author of the study and a doctoral student in sociology at Ohio State University.

Armour conducted the study with Dana Haynie, associate professor of sociology at Ohio State . Their results appear in the February 2007 issue of the Journal of Youth and Adolescence.

“The findings point out the importance of acting within normal bounds for your age group,” Haynie said. “Those who start having sex too young may not be prepared to deal with the potential emotional, social and behavioral consequences of their actions.”

The researchers used data from the National Longitudinal Study of Adolescent Health. An initial survey was conducted in 1994-95 of students from across the country in grades 7 to 12. These students attended 132 high schools and their “feeder” middle schools.

This study included students who reported they were virgins in this first survey. They were then surveyed again one year later, and a third time six years later in 2002.

In this study, the average age of sexual debut – age at first intercourse – was calculated for each school in the sample.

“That way, the respondents in the study are compared to the peers in their own school, rather than an arbitrary age that is deemed the average age for everyone,” Armour said.

The average age for sexual debut in this study ranged from 11.25 to 17.5 years of age, depending on the individual schools.

Adolescents in the sample who had their first sexual encounter about one year or more before average for their school (the exact length differed for each school) were considered early.

To determine rates of delinquency, students in the survey were asked how often in the past year they participated in a variety of delinquent acts, including painting graffiti, deliberately damaging property, stealing, or selling drugs.

The study found that youth who had their sexual debut between the first and second surveys showed a 58 percent increase in delinquency compared to those who remained virgins. But the increases were more pronounced for those who were younger than their peers when they first had sex.

The researchers found that of those respondents who had their first sexual experience between the first and second surveys, 9 percent had started significantly earlier than their peers, 58 percent were average, and 33 percent experienced sexual intercourse significantly later than others.

The researchers took into account a variety of factors that could affect how long adolescents wait to have sex, including race, family structure, socioeconomic status, school performance, depression, how close the teens felt to their parents, and other factors.

Armour said the link between early sex and delinquency probably has to do with the whole social context of the young adolescents' lives.

“If you're having sex a lot earlier than your friends, you may be hanging out with a new group of kids, ones who are probably older,” Armour said.

“Having sex brings with it this feeling of being an adult. They may feel like they can do things older kids do, and for some that may include delinquency.”

And these negative effects of early sex may last through adolescence and into early adulthood.

When the same respondents were surveyed again in 2002 – when most were between the ages of 18 and 26 – results showed that the age of first sex was still associated with levels of delinquency.

“The timing of events such as sexual activity can have profound consequences for adolescents, particularly when they occur prematurely,” Armour said.

On the other hand, delaying sex can have positive effects for adolescents.

“Those adolescents who waited longer than average may be developing friendships and relationships that can help protect them from potentially troublesome behaviors as they become young adults,” she said.

“Sex itself is not always a problem behavior,” Armour explained. “But the timing of sexual initiation does matter. Adolescents need to be at a stage when they are developmentally prepared for it.”