In the conservative US, the federal "abstinence only" program has pushed hard and some researches seem to obviously reach the needed cause-and-effect link, as shown by a study released in February 2007 at Ohio State University, which found that losing virginity earlier makes youngsters 20 % more prone to juvenile crime.

This is challenged by a new research led by Paige Harden, a doctoral candidate in psychology at the University of Virginia, who discovered that consensual sex during early teen or preteen years does not influence later the likelihood of delinquent behavior.
While the Ohio State study was based on information gathered from over 7,000 children involved in the National Longitudinal Study of Adolescent Health, the new research is much more subtle, going to a genetic level.

It has been based on over 500 pairs of twins, from the same pool investigated by the Ohio team and was able to tell apart which behavioral characteristics are determined by genes or the social environment.

Twin pairs share the same home environment, but their genetics vary: non-identical twins share the same DNA amount like ordinary brothers while identical twins develop from the same fecundated egg and have the same DNA. The team focused on identical twin pairs in which one twin started having sex at an earlier age than the other. But the "gigolo" twin did not turn out to be more criminal than the other.

"It turns out that there was no positive relationship between age of first sex and delinquency. The way to reconcile that with the previous evidence of a link is to conclude that some other factors are promoting both early sex and delinquency," said Harden.

Moreover, identical twins appeared to be more similar to one another concerning the ages at which they started their sex life, compared to fraternal twins, whose DNA sharing can be from about 0 % to about 100 % (most of them share 40-60 % of their genes, like in the case of normal brothers).

This research stresses that some genes, like some inducing higher impulsiveness and risk-taking, could rather form a link between early sex and increased risk of criminal activity.