WASHINGTON -- Children with attention deficit/hyperactivity disorder are more likely to smoke, drink and use illegal drugs, U.S. researchers reported on Sunday.

It could be because children with the disorder -- called ADHD -- have trouble paying attention, have problems at school and difficulty with relationships with friends and family. This, in turn, could make them susceptible to abusing drugs and alcohol, Reuters quoted the researchers as saying.

It also shows it is important to diagnose and treat ADHD early, the researchers write in the August issue of the Journal of Abnormal Psychology.

Psychologists Brooke Molina of the University of Pittsburgh School of Medicine and William Pelham of the State University of New York at Buffalo compared 142 teen-agers aged 13 to 18 who had been diagnosed with ADHD to 100 children without ADHD.

They looked for antisocial behavior reported by the teachers and parents and questioned the children.

Children with ADHD had a higher risk of abusing alcohol and heavier drugs, and were more likely to smoke, at younger ages, than non-ADHD children, they found. "Childhood ADHD symptoms, particularly the inattention dimension of ADHD, predicted later substance use to a greater degree than childhood antisocial behaviors,"