Alterations In Brain Dopamine Pathway Appears To Be Associated With Certain Symptoms Of ADHD

Main Category: ADHD
Also Included In: Neurology / Neuroscience;  Psychology / Psychiatry
Article Date: 15 Sep 2009 - 0:00 PDT

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Results from brain scans suggest an association between a reduction in the transmission of dopamine markers with symptoms of inattention for individuals with attention deficit/hyperactivity disorder (ADHD), according to a preliminary study in the September 9 issue of JAMA.

ADHD is a childhood psychiatric disorder that frequently persists into adulthood, and is estimated to affect 3 percent to 5 percent of the U.S. adult population, which makes it one of the most prevalent of all psychiatric disorders, according to background information in the article. Previous research has indicated that dopamine (a neurotransmitter essential for the normal functioning of the central nervous system) transmission is disrupted in some pathways of the brain in ADHD.

Nora D. Volkow, M.D., of the National Institute on Drug Abuse, Bethesda, Md., and colleagues conducted a study to determine whether there are abnormalities in the mesoaccumbens (site of the dopamine reward pathway in the mid-brain) in patients with ADHD. The researchers produced brain images with positron emission tomography (PET) to measure dopamine synaptic markers (transporters and D2/D3 receptors) in 53 nonmedicated adults with ADHD and 44 healthy controls.

Among the findings of the authors: "This study provides evidence in favor of the predicted disruption in the mesoaccumbens dopamine pathway in ADHD. With PET imaging, lower D2/D3 receptor and DAT [dopamine transporters] availability in those with ADHD than in the control group was documented in 2 key brain regions for reward and motivation (accumbens and midbrain)," they write. "The lower than normal D2/D3 receptor and DAT availability in the accumbens and midbrain regions supports the hypothesis of an impairment of the dopamine reward pathway in ADHD."

"Our findings of an association of the mesoaccumbens dopamine pathway with ADHD inattention symptoms may have clinical relevance. This pathway plays a key role in reinforcement-motivation and in learning stimuli-reward associations, and its involvement in ADHD supports the use of interventions to enhance the saliency of school and work tasks to improve performance. Both motivational interventions and contingency management have been shown to improve performance in ADHD patients. Also stimulant medications have been shown to increase the saliency of a cognitive task (motivation, interest) in proportion to the drug-induced dopamine increases in striatum [a region of the brain]," the researchers write.

JAMA. 2009;302[10]:1084-1091.

Source
Journal of the American Medical Association

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