Attention-deficit hyperactivity disorder often does not go away by adulthood, and children with ADHD are more likely to have other psychiatric disorders as adults, according to findings of a study.

Children with ADHD also appear more likely to commit suicide and to be incarcerated as adults, researchers reported in what is described as the first large, population-based study to follow children with ADHD.

"Only 37.5% of the children we contacted as adults were free of these really worrisome outcomes," William Barbaresi, MD, the study’s lead investigator who began the research while with the Mayo Clinic and now is with Boston Children’s Hospital, said in a news release. "That’s a sobering statistic that speaks to the need to greatly improve the long-term treatment of children with ADHD and provide a mechanism for treating them as adults."

The study is unique because it followed a large group of ADHD patients from childhood to adulthood, said Slavica Katusic, MD, an epidemiologist and Mayo Clinic’s lead researcher on the study.

ADHD is the most common neurodevelopmental disorder of childhood, affecting about 7% of all children and three times as many boys as girls. Most prior follow-up studies of ADHD have been small and focused on the severe end of the spectrum rather than a cross-section of the ADHD population, according to the researchers.

The researchers followed all children in Rochester, Minn., who were born between 1976 and 1982, were still in Rochester at age 5 and whose families allowed access to their medical records. The total study cohort was 5,718 children, including 367 diagnosed with ADHD. Of this group, 232 participated in the follow-up study. About three-quarters received ADHD treatment as children.

At follow-up, the researchers found 29% of children with ADHD still had ADHD as adults.

Of children with ADHD, 57% had at least one other psychiatric disorder as adults, compared with 35% of those who did not have childhood ADHD. The most common disorders were substance abuse/dependence, antisocial personality disorder, hypomanic episodes, generalized anxiety and major depression.

Of the children who still had ADHD as adults, 81% had at least one other psychiatric disorder, as compared with 47% of those who no longer had ADHD.

Seven of the 367 children with ADHD (1.9%) had died when the study began, including three from suicide. Of the 4,946 children without ADHD whose outcomes could be ascertained, 37 children (0.07%) had died, five by suicide.

Ten adults who had childhood ADHD (2.7%) were incarcerated when the study began.

"We suffer from the misconception that ADHD is just an annoying childhood disorder that’s overtreated," Barbaresi said. "This couldn’t be further from the truth. We need to have a chronic disease approach to ADHD as we do for diabetes. The system of care has to be designed for the long haul."

Barbaresi said the study findings may underestimate the bad outcomes of childhood ADHD. Most of those studied were white and middle-class, with good educations and access to healthcare. "One can argue that this is potentially a best-case scenario," Barbaresi said. "Outcomes could be worse in socioeconomically challenged populations."

He advises parents of children with ADHD to ensure their children receive high-quality treatment, and continue receiving treatment as they enter adolescence. Children also should be assessed for learning disabilities and monitored for conditions associated with ADHD, including substance use, depression and anxiety.

The study was published March 4 on the website of the journal Pediatrics. The study abstract is available at http://pediatrics.aappublications.org/content/early/2013/02/26/peds.2012-2354.abstract.