NEW YORK — About 30 percent of Americans by age 23 have been arrested at least once for something other than a traffic violation, increasing their chances of professional and family strife, researchers say.

By age 18, about 16 percent to 27 percent of teenagers have been arrested at least once, according to a study released Monday in the journal Pediatrics.

Youths with arrest records have lower earnings, longer periods of unemployment and a greater risk of family conflict than those without, according to the study. The previous best estimate of arrests for nontraffic offenses, done in 1965, showed that about 22 percent of U.S. adults had been apprehended at least once by age 23.

The increase may be a reflection of the justice system becoming more punitive and more aggressive in its reach during the last half-century, the researchers said. Arrests for drug-related offenses, for example, have become far more common, as have zero-tolerance policies in schools.

The study did not look at racial or regional differences, but other research has found higher arrest rates for black men and for youths living in poor urban areas.

Criminal-justice experts said the 30.2 percent figure was especially notable at a time when employers, aided by the Internet, routinely conduct criminal background checks on job candidates.

"This estimate provides a real sense that the proportion of people who have criminal-history records is sizable and perhaps much larger than most people would expect," said Shawn Bushway, a criminologist at the State University of New York at Albany and a co-author of the study.

The study analyzed data collected as part of the federal government's National Longitudinal Survey of Youth. The 7,335 participants were nationally representative and ranged in age from 12 to 16 when they were enrolled in the survey in 1996.

The first interviews were conducted in 1997. The surveys continued through 2008 asking a variety of questions about participants' activities including whether they'd been arrested by police. Researchers estimated the rate of those who didn't respond.

The researchers found that the probability of a first arrest accelerated in late adolescence and early adulthood — at 18, 15.9 percent of the participants reported having been arrested — and then began to flatten out as the youths entered their 20s.

Robert Brame, a professor of criminal justice and criminology at the University of North Carolina, Charlotte, and the lead author of the study, said he hoped the research would alert physicians.

"We know that arrest occurs in a context," Brame said. "There are other things going on in people's lives at the time they get arrested, and those things aren't necessarily good."

If doctors can intervene, he added, "It can have big implications for what happens to these kids after the arrest."

The increase in arrest rates is primarily in ages 19 through 22, and may reflect the delay in marriage and careers as more young people seek higher education, increasing the length of "adolescence," Brame said.