The Gender Gap
While ADHD is thought to occur more often in boys than in girls, there may be another reason why four times as many boys are diagnosed with the disorder. Girls with ADHD tend to demonstrate more subtle symptoms, although little research has been done to explain why. A newly launched Kennedy Krieger study aims to determine whether ADHD is associated with different brain characteristics in girls than in boys.
Funded by a five-year, $1.8 million National Institutes of Health grant, the study attempts to connect impairments caused by ADHD with anomalies in size and composition of the regions of the brain responsible for those characteristics. To do so, researchers are recruiting 200 boys and girls between the ages of nine and 11 1/2, both with and without ADHD. The children complete tasks assessing those skills often impaired by ADHD.
The study hypothesizes that while both girls and boys with ADHD will have greater impairment in attentiveness, working memory and response preparation than the children in the control group, girls with ADHD will not have as many problems with impulse control. At the same time, researchers expect the girls to have more significant attention, working memory, and response preparation difficulties than the boys.
Scientists will then compare the results of those tests with MRIs of the children's brains. Kennedy Krieger's Dr. Stewart Mostofsky has already confirmed a volume difference in the frontal lobes of boys with ADHD from those without the disorder. The current study will examine subdivisions of the frontal lobes and other more specific brain regions. Researchers expect to find that girls have smaller volumes in the regions responsible for attention and memory than the boys.
"I want to be able to document the features and brain circuitry of ADHD that are distinctive in girls because that gives us the power to recognize more subtle predictors and indicators of the disorder," says Dr. Martha Denckla, principal investigator of the study.
Uncovering those markers may make it easier for clinicians to diagnose ADHD at an earlier age, says Dr. Mark Mahone, who is also contributing to the study. "Early diagnosis is important because, with any disorder, the later you identify it, the more vulnerable your outcome is," says Dr. Mahone.
Because the symptoms of ADHD exhibited by girls tend to be less disruptive than those exhibited by boys, girls tend to be diagnosed later. "Girls remain cosmetically well-behaved in school, and their disorder doesn't become obvious until the "tween" age, when there's more of a burden placed on them in terms of personal responsibility," says Dr. Denckla. Those delayed diagnoses can be costly: Although fewer girls than boys are diagnosed with ADHD, girls with the disorder have much higher rates of depression and drug use than boys with ADHD.
"Girls with ADHD have a history of failure and frustration due to their ADHD, and have many more social problems than boys," says Dr. Denckla. "There's no equivalent of boys will be boys' that applies to girls the behavior standard is set much higher. Getting these girls treatment earlier could ward off the crises many experience in adolescence."