Children with ADHD symptoms tend to fare worse as adults than do kids without problems in school, according to the longest follow-up study of the disorder to date.

They have less education and lower income, on average, and higher rates of divorce and substance abuse, according to findings released today in the Archives of General Psychiatry.

"A lot of them do fine, but there is a small proportion that is in a great deal of difficulty," said Rachel Klein, a professor of child and adolescent psychiatry at NYU Langone Medical Center in New York. "They go to jail, they get hospitalised."

Klein and her colleagues followed 135 white men who had been rated hyperactive by their school teachers back in the 1970s and referred to the hospital. According to Klein, the children did not have aggressive or antisocial behaviours and would have been diagnosed with attention deficit hyperactivity disorder today.

They all came from ordinary middle-class homes, Klein said, and had "well-meaning" parents. When the boys were 18, the researchers established a comparison group of age-matched white boys who had visited their medical centre for unrelated reasons and had not had any problems at school.

Based on interviews done when the men were 41 years old, on average, Klein's team found that those who'd had ADHD symptoms as kids left school 2.5 years before the comparison group. Only four per cent had higher degrees versus 29 per cent of their peers.

In both groups, salaries went as high as $1.5 million a year. But in the comparison group, the average salary was about $175,000, compared to $93,000 in the troubled children.

More than one in five of the hyperactive boys were diagnosed with ADHD three decades later, versus one in 20 in the comparison group. And about a third had been in jail at some point - about three times the comparison rate.

They were also more likely to be divorced, abuse drugs and be labeled with antisocial behaviour disorder. However, they weren't more likely to have mood or anxiety disorders.

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