Links ADHD Cognitive and Behavioral Problems To Genetic and Environmental
1, 2006 CINCINNATI - A new study indicates that cognitive and behavioral
problems that underlie attention deficit hyperactivity disorder,
or ADHD, are due to a complex interplay of genes and the environment.
The Cincinnati Children's Hospital Medical Center study is the first
to examine how genes, toxins and gender interact to shape ADHD.
study shows that certain groups of children have an increased sensitivity
to environmental exposures," says Tanya Froehlich, MD, a physician
at Cincinnati Children's and the study's lead author. "More
studies like this one are needed to help set exposure standards
that adequately protect the most susceptible members of society."
study was presented at 10:15 am Pacific time Monday, May 1, at the
annual Pediatric Academic Societies Annual Meeting in San Francisco.
Cincinnati Children's researchers examined the impact of lead exposure
on executive function -- the ability to plan and organize activities
and behaviors. Executive function is impaired in individuals with
ADHD. They particularly wanted to determine whether lead's effects
are influenced by an individual's underlying genetic and biological
make-up, including the impact of gender and variations in the DRD4
dopamine receptor gene. The DRD4 receptor helps regulate brain levels
of dopamine, a chemical in the brain that is essential for attention
and cognition, and variations in DRD4's composition have been linked
study findings indicate that increasing lead exposure is linked
to impairment on a number of executive functions, including planning,
memory span and attentional flexibility (the ability to revise one's
plan or strategy in the face of obstacles or new information). However,
certain genetic and biological factors seemed to predispose an individual
to the negative effects of lead exposure. For instance, only children
with certain variations of the DRD4 gene seemed vulnerable to lead's
adverse effects on attentional flexibility.
addition, increasing lead exposure impaired performance in both
planning and attentional flexibility in boys more than in girls.
This suggests that, for these executive functions, boys are more
vulnerable to the adverse affects of lead exposure," says Dr.
Froehlich. "This is also consistent with the established fact
that boys have higher rates of ADHD than girls."
researchers studied 172 children who were enrolled in a community-based
study of low levels of lead exposure. Blood lead levels were assessed
during infancy and early childhood. At age 5, children took standardized,
ADHD-related executive function tests.
study offers a model for examining how genes and environmental toxins
interact to shape ADHD, and demonstrates that important effects
may be obscured or over-generalized if the joint contributions of
these factors are not considered," says Dr. Froehlich. "Such
studies can help us understand the underlying causes of neuropsychological
disorders, and why certain groups may be more prone to ADHD than
Children's is a 475-bed institution devoted to bringing the world
the joy of healthier kids. Cincinnati Children's is dedicated to
transforming the way health care is delivered by providing care
that is timely, efficient, effective, family-centered, equitable
and safe. It ranks third nationally among all pediatric centers
in research grants from the National Institutes of Health. The Cincinnati
Children's vision is to be the leader in improving child health.
For more information, visit www.cchmc.org
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