Adult ADHD
Visual Abstract
Evaluating dopamine reward pathway in ADHD: clinical implications
Dopamine Receptors and ADHD
Nora D Volkow , Gene-Jack Wang, Scott H Kollins, Tim L Wigal, Jeffrey H Newcorn, Frank Telang, Joanna S Fowler, Wei Zhu, Jean Logan, Yeming Ma, Kith Pradhan, Christopher Wong, James M Swanson
Summarized by:
August 31, 2023
study source
JAMA
Sep 2009
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What they studied
This study compared the amounts and locations of dopamine receptors in those with ADHD.
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What they found
Adults with ADHD tended to have fewer dopamine receptors, particularly in the reward and regulatory centers of the brain.
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What this means
These results provide a biological explanation for some ADHD symptoms.
Evaluating dopamine reward pathway in ADHD: clinical implications
Objectives
ADHD is a common psychiatric condition among children and adults. It is typically characterized by symptoms involving attention, hyperactivity, and impulsivity.
It has also been associated with a wide range of cognitive effects, including changes to how we handle rewards and motivation.
This study aimed to understand the biological basis of reward and motivation symptoms in ADHD through brain imaging.
Study Quote
Context: Attention-deficit/hyperactivity disorder (ADHD)--characterized by symptoms of inattention and hyperactivity-impulsivity--is the most prevalent childhood psychiatric disorder that frequently persists into adulthood, and there is increasing evidence of reward-motivation deficits i...
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Methods
Researchers used PET scans to evaluate the location and quantity of dopamine receptors in adults with ADHD compared to adults without ADHD.
This technique allows researchers to directly compare and evaluate differences in brain structure within the systems responsible for motivation and reward.
Study Quote
Design, setting, and participants: We used positron emission tomography to measure dopamine synaptic markers (transporters and D(2)/D(3) receptors) in 53 nonmedicated adults with ADHD and 44 healthy controls between 2001-2009 at Brookhaven National Laboratory.
Main ou...
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Results
The results showed significant differences in the brains of those with ADHD.
Brain imaging showed fewer dopamine receptors in the reward centers of the brains of those with ADHD.
Dopamine is the neurotransmitter responsible for our feelings of joy when we accomplish something.
A study on dopamine receptors in the brain found that those with ADHD had fewer receptors in the reward centers of the brain than similar adults without ADHD.
These differences were found in the brain's reward center, the location where dopamine is produced, and in the hypothalamus, which is responsible for regulating and maintaining the body's critical processes through hormones.
Study Quote
Results: For both ligands, statistical parametric mapping showed that specific binding was lower in ADHD than in controls (threshold for significance set at P < .005) in regions of the dopamine reward pathway in the left side of the brain. Region-of-interest analyses corroborated these f...
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Conclusions
The researchers concluded that these results provide a potential biological explanation for why does with ADHD have difficulty paying attention, particularly for tedious tasks.
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In our study, the D2/D3 receptor measures in accumbens were correlated with the dimension of attention, which would implicate the dopamine reward pathway in the symptoms of inattention in ADHD. This could provide an explanation of why the attentional deficits in individuals with ADHD are most evident in tasks that are considered boring, repetitive, and uninteresting (ie, tasks or assignments that are not intrinsically rewarding).
Dopamine is also involved in drug abuse—many illicit drugs work by triggering the release of dopamine.
Because of the differences in dopamine receptors in this study, the authors' theory is that this may play a role in the higher drug abuse rates among those with ADHD.
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Finally, because a low number of dopamine D2/D3 receptors in the nucleus accumbens have been associated with a greater risk for drug abuse, future work should determine if the lower than normal D2/D3 receptor availability in the accumbens region in ADHD underlies the higher vulnerability for substance abuse in this population.
This is consistent with studies examining substance abuse among those with ADHD:
Study Quote
Conclusion: A reduction in dopamine synaptic markers associated with symptoms of inattention was shown in the dopamine reward pathway of participants with ADHD.