WEDNESDAY, Feb. 25 (HealthDay News) -- A new study suggests it's possible that too much work might turn a youngster into a juvenile delinquent.

Researchers found that fifth-graders who worked the most at jobs such as baby-sitting and newspaper routes were the most likely to smoke, drink and get into fights.

The findings don't prove that overwork directly leads to trouble, but they raise questions about the value of work, said study author Rajeev Ramchand, an associate behavioral scientist at the Rand Corp.

"We know [working] can be positive, but the time they spend working is associated with worse outcomes," he said.

According to the study, previous research has suggested that older kids who work are more likely to abuse substances and get in trouble with the law. The study is apparently the first of its kind to look at work and younger kids.

The study authors examined the results of a 2004-2006 survey of 5,147 fifth-graders and their parents in Birmingham, Ala., Houston and Los Angeles. The findings were published in the April issue of the American Journal of Preventive Medicine.

After adjusting statistics from the findings to account for factors such as household income, the researchers found that the fifth-graders with jobs were two times more likely than other children to have used alcohol within the past 30 days. The rate was two times higher for tobacco use and three times higher for marijuana use. Those who worked were also 1.5 times more likely to have ever been in a fight and two times more likely to have run away from home.

The researchers defined working as having a for-pay job such as yard work, door-to-door candy sales and baby-sitting. About one in five fifth-graders said they had a job.

Why might a job be a problem? It's possible that parents may stop monitoring their children as much when they're working, Ramchand said.