Hunt for attention deficit/hyperactivity disorder Genes
Existing evidence suggests that genetic risk factors are critical to the development of attention deficit/hyperactivity disorder. Experts at Duke University Medical Center say that identification of the genes responsible is the first step towards earlier detection, prevention and, in the future, better treatments for attention deficit/hyperactivity disorder.
Allison Ashley-Koch, Ph.D., is a geneticist at the Duke Center for Human Genetics. She says attention deficit/hyperactivity disorder is believed to be one of the most heritable of all psychiatric conditions.
Siblings of individuals with AD/HD are about four times more likely to develop attention deficit/hyperactivity disorder than individuals with no family history of the disorder, she said. Similarly, a number of parents of individuals with AD/HD also suffer symptoms. However, adults often fail to recognize their own symptoms until after their child is diagnosed.
"It's estimated that up to 90 percent of the risk for developing attention deficit/hyperactivity disorder stems from genetic factors," Ashley-Koch said.
"AD/HD is a complex disorder likely influenced by a number of genes - some more important than others," she continued. "We expect these genes interact with each other and with environmental factors to trigger the development of attention deficit/hyperactivity disorder."
To tease out key attention deficit/hyperactivity disorder genes and important gene-gene and gene-environment interactions, the Duke Center for Human Genetics is enrolling children with attention deficit/hyperactivity disorder between the ages of 5 and 12 in a genetic study.
The research team collects detailed family, medical and environmental risk factor histories. Participants are also asked to complete a series of psychological and behavioral assessments. Blood samples are collected from the children with attention deficit/hyperactivity disorder and their parents, whenever possible. Samples may also be collected from siblings and other relatives, regardless of whether or not they show signs of attention deficit/hyperactivity disorder.
The team will follow study participants over time as their symptoms evolve, Ashley-Koch said. "We hope to not only identify candidate genes that predispose people to attention deficit/hyperactivity disorder, but also to identify genes that may differentiate distinct forms of the condition."
Three subtypes of attention deficit/hyperactivity disorder are recognized, she said. Some people exhibit primarily inattentive symptoms while others exhibit primarily hyperactive-impulsive symptoms. Still others struggle with both.
In addition, psychological conditions - such as anxiety, depression or oppositional defiance disorder -- often overlap with attention deficit/hyperactivity disorder symptoms, adding another layer of complexity, Ashley-Koch said.
"People with attention deficit/hyperactivity disorder can follow different trajectories over time," Ashley-Koch said. For example, a child may start out hyperactive, but then grow out of that particular symptom. "Separate genetic risk factors may underlie different aspects of the disorder."
The AD/HD study represents a collaboration between the Duke Center for Human Genetics, the Duke attention deficit/hyperactivity disorder Clinic and the University of North Carolina-Greensboro. To learn more about the genetics of AD/HD and ongoing studies, please contact the CHG at email@example.com or toll-free at 1-866-DUK-ADHD (1-866-385-2343).