MONDAY, April 19 (HealthDay News) -- An interaction of genetics and psychology may be the cause of attention-deficit hyperactivity disorder (ADHD), say U.S. researchers.

Their study of 304 youths found that ADHD symptoms were more common in children and teens with high or low activity levels of the neurotransmitter serotonin and who blame themselves for conflict between their parents.

"To date, studies have mostly focused on the effects of genetic and environmental influences on ADHD separately," wrote Molly Nikolas, of Michigan State University, and colleagues. "Our work examines the interaction between a specific gene variant and a family environmental risk factor in order to determine their roles in the development of ADHD via behavioral and emotional dysregulation in children."

The genetic region examined by the researchers is 5HTTLPR, which is responsible for regulating the production of a protein that transports serotonin. Previous studies have linked this area to a number of personality traits and neuropsychiatric disorders.

"Overall, these results complement growing evidence suggesting that 5HTTLPR variants confer a liability for ADHD that is activated in particular environments, rather than conferring risk for ADHD directly," the researchers concluded.

The study was published April 15 in the journal Behavioral and Brain Functions.

More information

The U.S. National Institute of Mental Health has more about ADHD.