"I remember being very embarrassed I couldn't finish," Luper, 18, said. "I didn't tell any of my friends."

A study that was begun that school year in Johnston County -- one of the largest ever conducted anywhere on attention-deficit hyperactivity disorder -- prompted Luper's parents to consult a doctor, who formally diagnosed her with ADHD.

A decade after that original study, researchers are back. They hope to clarify how the disorder evolves as students navigate their teenage years and adulthood.

Luper, who stopped taking ADHD medication last year as a high school junior, had doubts about taking part in the follow-up study. After weeks of consideration, she decided to participate.

Researchers say they need her help. The closest example of a large community-based study of ADHD -- outside of the Johnston County one -- dates back to the 1960s in California. Researchers at the National Institute of Environmental Health Sciences in Research Triangle Park, UNC-Chapel Hill and Duke University chose Johnston County because of its diversity and manageable size.

Most of what is known about ADHD stems from smaller clinical studies, predominantly of Caucasian boys with the hyperactive form of the disorder. Much less is known about ADHD in young adults, especially females, African-Americans and children with the inattentive type of ADHD.

"This information is crucial for doctors, therapists, teachers or social workers trying to help youth with ADHD," said Andrew Rowland, now an epidemiology professor at the University of New Mexico.

The original study, involving 6,099 first- through fifth-graders in all Johnston County elementary schools, revealed some alarming initial results. Parent surveys showed that about 10 percent of the elementary school students had been diagnosed with ADHD. The finding challenged previous studies citing estimates that 3 percent to 5 percent of children have ADHD.

The study also indicated that 7 percent of children were taking stimulant medication to help them calm down or concentrate. Many of the children taking stimulants, however, continued to show symptoms of ADHD, suggesting problems with the doses or with how they were taking the medication. ADHD remains hotly debated because some see it as a result of poor parenting, not a disorder, and they worry that the nation is excessively medicating millions of youngsters.

In the long run?

Rowland said hundreds of studies have shown that stimulants, such as Ritalin and Concerta, help children with ADHD concentrate in the short run.

"What is not known," he said, "is how well those medications work over the long term and if they make a difference in important everyday areas like grades, sleep, ability to make friends or get along with family members."

Luper said she began taking Ritalin in the fourth grade. She swallowed a pill with breakfast before school. The drug made her queasy. It made her feel as if she were the only one in a room. Rather than chat with friends as she might normally want to, she would just feel like sitting quietly. But the sacrifice was worth it.

Before that point, anything would distract her -- classmates talking, paper being crumpled, a pin dropping.

"I was making better grades than I would without it," she said. "I knew in 10 years it wouldn't matter how I had felt -- it would matter what I'd learned."

Focused, but different

Denise Luper, a teacher at North Johnston High School, said she didn't see the full effect drugs had on her daughter until she taught her SAT prep in ninth grade. By then, Paula had switched to another medication, Concerta.

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