If difficult behavior in young children is prolonged or especially intense, the child may have conduct disorder, a childhood psychiatric problem that could be a harbinger of antisocial behavior, according to a recent study.

Researchers at Washington University School of Medicine in St. Louis found that certain symptoms of conduct disorder indicate problems are likely to continue as kids reach school age. They recommend that children who exhibit these symptoms -- among them, high-intensity defiant behavior, aggression and destruction of property -- be referred to mental health professionals for evaluation and possible intervention.

"Previously, we did not understand the empirical differences between normal disruptive behaviors in preschoolers - like temper tantrums, for example -- and behaviors that signal problems," Joan L. Luby, senior investigator of the study, said in a statement. "If you went to your pediatrician and said, 'My 3-year-old is having tantrums,' the pediatrician wouldn't tell you to see a psychiatrist."

Based on their findings, researchers found that those who exhibited high-intensity defiant behavior, aggression toward people or animals, high-intensity destruction of property, peer problems and deceitfulness, including stealing, were likely to have conduct disorder. Having those symptoms also made it more likely they would carry the disorder into elementary school.

"We characterize a symptom as high-intensity when it's really 'high-pitched' -- so just how severe the anger is," Luby said. "Other factors that would qualify a symptom as high-intensity would hinge on how frequently the behavior occurs and the context in which it occurs. A high-intensity symptom is one that is very acute or severe, occurs over a long duration of time and happens in a number of different contexts."

Children who had high-intensity symptoms as preschoolers were likely to have conduct disorder, and those symptoms also tended to predict conduct disorder when they reached school age.

Researchers believe that the best chance young children have to avoid recurring problems is early diagnosis and treatment.

The findings are detailed in The Journal of Pediatrics.