FSU psychology professors Jeanette Taylor and Chris Schatschneider, FSU doctoral student Kelly Cukrowicz and University of Minnesota Professor William Iacono found that children with ADHD or conduct disorder had more negative emotions - aggressiveness, tension and feelings of being exploited, unlucky or poorly treated - and lower constraints - a tendency to break rules and engage in thrill-seeking behavior - than children with neither of the disorders. Not surprisingly, those children who have both ADHD and conduct disorder had the most extreme personality profiles.

"This helps us to understand that personality is part of the bigger picture of these disorders," Taylor said. "That could help with initial assessments or lead to unexpected discoveries or potential interventions. We're saying to researchers and clinicians, 'Think about personality when you look at these issues.' "

The study, published in the Journal of Child Psychology and Psychiatry, is the first to investigate personality trait patterns among children who have ADHD, conduct disorder or a combination of both. It is important to learn more about the co-occurrence of ADHD and conduct disorder because the consequences are so severe, Taylor said.

"It's more than the sum of its parts," she said, explaining that children and adolescents with a combination of the two disorders are at much higher risk of school failure, criminal activity, substance abuse and depression. Previous studies have indicated that between 15 to 35 percent of children with ADHD also have conduct disorder.

Between 3 percent and 5 percent of U.S. school age children are estimated to have ADHD, a disorder that encompasses symptoms of hyperactivity, inattention or impulsivity. Conduct disorder affects about 13 percent of children and adolescents and is characterized by severe misbehavior including chronic lying, setting fires, destroying property or hurting animals.

The researchers analyzed personality data from 1,438 sets of same-sex, reared-together 11-year-old and 17-year-old male and female twins who participated in the Minnesota Twin Family Study. The rate of ADHD, conduct disorder and the co-occurrence of both was about the same as is found in the general population, Taylor said. Those who did not have symptoms of the disorders served as the control group.

The connection between personality and the disorders is clear, but more research will have to be done to determine whether the personality traits are shaped by the psychological disorders or vice versa.

"Developmentally, it makes sense that the personality comes first," she said. "But to say that one causes the other is too simplistic. I think they become intertwined."

Note: If no author is given, the source is cited instead.

• Attention Deficit Disorder
• Children's Health
• Mental Health Research

• ADD and ADHD
• Borderline Personality Disorder
• Psychiatry

• Adult attention-deficit disorder
• Autistic spectrum
• Pyromania
• Personality disorder
• Antisocial personality disorder
• Learning disability