(HealthCentersOnline) - Results from a recent brain-imaging study call into question the relationship between dopamine, its associated proteins and the presence of attention deficit hyperactivity disorder (ADHD). Dopamine is a neurotransmitter important in thinking, motivation, short-term memory and some emotions, as well as immune function and motor control.
It was previously believed that unusually high levels of a brain protein responsible for transporting dopamine in some parts of the brain indicated the presence of ADHD. However, researchers found lower levels of these proteins in ADHD patients when measured against the control group.
"These results suggest that dopamine transporter levels alone cannot account for the severity of symptoms of inattention in ADHD," lead study author Nora Volkow said in a recent news release.
ADHD is a set of chronic conditions marked by an inability to pay attention, hyperactivity and impulsive acts. It begins in childhood and can affect all areas of a child's life. Between 3 and 5 percent of school-aged children—or about 2 million children in the United States—have ADHD, according to the National Institute of Mental Health (NIMH). Boys outnumber girls by at least a 3 to 1 ratio, according to National Mental Health Association.
For many years, controversy has surrounded ADHD as some experts have differed over exactly what constitutes the disorder.
Copyright 2009 NBC Health
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