Signs of ADHD evident by preschool, expert says

(HealthDay) -- One out of 11 school-aged children is diagnosed with attention-deficit/hyperactivity disorder (ADHD), and up to 40 percent of those kids may display symptoms in preschool, an expert says.

Recognizing and treating the disorder early is important because ADHD has a profound effect on learning and academic development, says Dr. Mark Mahone, director of the department of neuropsychology at Kennedy Krieger Institute in Baltimore.

"Children whose symptoms begin in early childhood are at the highest risk for academic failure and grade repetition," Mahone noted.

"Research shows that children with ADHD have abnormal brain development, meaning that ADHD has a biological basis that often makes it a lifelong condition," he added in an institute news release.

Parents should pay close attention to the behavior of their young children, Mahone said. He added that in children aged 3 to 4, the following behaviors are often associated with a diagnosis of ADHD by the time children reach school age:

• Avoids or dislikes activities that require more than one to two minutes of concentration
• Loses interest in activities after a few minutes
• Talks a lot more and makes more noise than other children the same age
• Climbs on things despite being told not to
• Unable to hop on one foot by the age of 4
• Almost always restless and insists on getting up after being seated for only a few minutes
• Acts fearless, which results in dangerous situations
• Warms up to strangers too quickly
• Behaves aggressively with friends
• Has been injured after moving too fast or running after being told to slow down

Useing neuroimaging, Mahone and his colleagues recently found that children with ADHD have a smaller caudate nucleus (a small structure in the brain associated with thinking and motor control) than other children their age. They hope their research leads to earlier interventions for children with ADHD to improve educational outcomes.

The causes of ADHD aren't really known, although studies suggest that genes play a role. Scientists are also looking into whether brain injuries, diet and social environment contribute to the disorder.