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Attention Deficit Hyperactivity Disorder (ADHD): The Role of Dopamine

What is attention deficit hyperactivity disorder?

Highlights

  1. ADHD is common.
  2. People with ADHD may use dopamine less efficiently than people who don’t have ADHD.
  3. Genetics may also be a risk factor for ADHD.

Attention deficit hyperactivity disorder (ADHD) is a mental disorder. People with ADHD have difficulty maintaining attention or have episodes of hyperactivity that interfere with their daily life. People sometimes refer to it as attention deficit disorder (ADD), but ADHD is the medically accepted term.

ADHD is common. Researchers in one research study estimate that 6 to 9 percent of children and 3 to 5 percent of adults in the United States have ADHD.

ADHD usually begins in childhood. It often continues through adolescence and sometimes adulthood. Children and adults with ADHD typically have more difficulty focusing than people who don’t have ADHD. They may also act more impulsively than their peers. This may make it difficult for them to perform well in school or work as well as the general community.

Learn more: The history of ADHD »

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Connection

Dopamine transporters and ADHD

Underlying issues with the brain are likely to be the underlying cause of ADHD. No one knows exactly what causes a person to have ADHD, but some researchers have looked at a neurotransmitter called dopamine as a possible contributor to ADHD. Dopamine allows us to regulate emotional responses and take action to achieve specific rewards. It’s responsible for feelings of pleasure and reward.

Scientists have observed that lower levels of dopamine are associated with symptoms of ADHD. Researchers believe this is because neurons in the brain and nervous system have higher concentrations of proteins called dopamine transporters. These protein transporters temporarily prevent dopamine from going on to the next cell. This lessens the effects of dopamine. The concentration of these proteins is known as dopamine transporter density (DTD).

Higher levels of DTD may be a risk factor for ADHD. Just because someone has high levels of DTD, however, doesn’t mean they have ADHD. Doctors will typically use a holistic review to make the formal diagnosis.

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Research

What does the research say?

One of the first studies that looked at DTD in humans was published in 1999. The researchers noted a 70 percent increase in DTD in six adults with ADHD compared to study participants who didn’t have ADHD. This suggests that increased DTD may be a useful screening tool for ADHD.

Since this early study, research has continued to show an association between dopamine transporters and ADHD. A recent study looked at research showing that the dopamine transporter gene, DAT1, may influence ADHD-like traits. They surveyed 1,289 healthy adults. The survey asked about impulsivity, inattention, and mood instability, which are the three factors that define ADHD. The researchers concluded that DAT1 might influence ADHD-like symptoms in the general population.

DTD and genes such as DAT1 aren’t definite indicators of ADHD. Most clinical studies have included only a small number of people. More studies are needed before firmer conclusions can be drawn. Additionally, some researchers argue that other factors contribute more to ADHD than dopamine levels and DTD.

One study found that that the amount of gray matter in the brain may contribute to ADHD more than levels of dopamine. Another research study from 2006 showed that dopamine transporters were lower in parts of the left brain in participants that had ADHD.

With these somewhat conflicting research findings, it’s hard to say if higher levels of DTD always indicate ADHD. Nonetheless, the research showing an association between ADHD and lower levels of dopamine as well as higher levels of DTD suggests that dopamine could be a possible treatment for ADHD.

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Treatment

How is ADHD treated?

Medications that increase dopamine

Many medications for treating ADHD work by increasing dopamine and stimulating focus. These medications are typically stimulants. They include amphetamines such as Adderall and methylphenidate (Concerta, Ritalin).

Learn more: Adderall vs. Ritalin: What’s the difference? »

These medications work by increasing dopamine levels in the brain. They do this by targeting dopamine transporters and increasing dopamine levels.

Some people believe that taking a high dosage of these medications will lead to greater focus and attention. This is not true. If your dopamine levels are too high, this can make it difficult for you to focus.

Other treatments

In 2003, the FDA approved the use of non-stimulant drugs to treat ADHD. Additionally, doctors recommend behavior therapy for both the person who has ADHD as well as their loved ones. Behavior therapy typically involves going to a board-certified therapist for counseling.

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Causes

Other causes of ADHD

Scientists aren’t certain what causes ADHD. Dopamine and its transporters are just two potential factors. Researchers have observed that ADHD tends to be more common in families. This is explained in part because many different genes may contribute to the incidence of ADHD.

Several lifestyle and behavioral factors may also contribute to ADHD. They include:

  • exposure to toxic substances, such as lead, during infancy and childbirth
  • the mother smoking or drinking during pregnancy
  • a low birth weight
  • complications during childbirth
  • high levels of neglect or abuse
  • a lack of social environment
  • excess sugar
  • food additives
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Takeaway

Takeaway

The association between ADHD, dopamine, and DTD is promising. Several effective medications used to treat the symptoms of ADHD work by increasing the impact of dopamine on the body. Researchers are also still investigating this association.

That being said, dopamine and DTD aren’t the only underlying causes of ADHD. Researchers are investigating new possible explanations such as the amount of gray matter in the brain.

If you have ADHD or suspect you do, talk to your doctor. They can give you the proper diagnosis, and you can start on a plan that may include drugs and natural methods that increase dopamine.

You can also do the following to increase your dopamine levels:

  • Try something new.
  • Make a list of small tasks and complete them.
  • Listen to music you enjoy.
  • Avoid foods with excess fat and sugar.
  • Exercise regularly.
  • Meditate and do yoga.
Article resources
  • Cook, E. H., Stein, M. A., Krasowski, M. D., Cox, N. J., Olkon, D. M., Kieffer, J. E., & Leventhal, B. L. (1995, April). Association of attention-deficit disorder and the dopamine transporter gene [Abstract]. American Journal of Human Genetics56(4), 993-998. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1801209/  
  • del Campo, N., Fryer, T. D., Hong, Y. T., Smith, R., Brichard, L., Acosta-Cabronero, J., . . . Muller, U. (2013, October 25). A positron emission tomography study of nigro-striatal dopaminergic mechanisms underlying attention: Implications for ADHD and its treatment. Brain: A Journal of Neurology, 136, 3252-3270. Retrieved from http://brain.oxfordjournals.org/content/136/11/3252.full
  • Dopheide, J. A. & Pliszka, S. R. (2009, June). Attention‐deficit‐hyperactivity disorder: An update [Abstract]. Pharmacotherapy: The Journal of Human Pharmacology and Drug Therapy29(6), 656-679. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/19476419
  • Dougherty, D. D., Bonab, A. A., Spencer, T. J., Rauch, S. L., Madras, B. K., & Fischman, A. J. (1999, December). Dopamine transporter density in patients with attention deficit hyperactivity disorder [Abstract]. The Lancet354(9196), 2132-2133. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/10609822
  • Jeong, S. H., Choi, K. S., Lee, K. Y., Kim, E. J., Kim, Y. S., & Joo, E. J. (2015, June). Association between the dopamine transporter gene (DAT1) and attention deficit hyperactivity disorder-related traits in healthy adults [Abstract]. Psychiatric genetics25(3), 119-126. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/25915480
  • Madras, B. K., Miller, G. M., & Fischman, A. J. (2005, June). The dopamine transporter and attention-deficit/hyperactivity disorder [Abstract]. Biological psychiatry, 57(11), 1397-1409. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/15950014
  • The ADHD genetic research study at the national institute of health and the National Human Genome Research Institute. (2014, March 17). Retrieved from https://www.genome.gov/10004297/the-adhd-genetic-research-study-at-nih/
  • Tripp, G. & Wickens, J. R. (2008, June 28). Research review: Dopamine transfer deficit: A neurobiological theory of altered reinforcement mechanisms in ADHD. Journal of Child Psychology and Psychiatry49(7), 691-704. Retrieved from http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7610.2007.01851.x/full
  • Volkow, N. D., Wang, G. J., Kollins, S. H., Wigal, T. L., Newcorn, J. H., Telang, F., . . . Swanson, J. M. (2009, September 9). Evaluating dopamine reward pathway in ADHD: Clinical implications. Journal of the American Medical Association302(10), 1084-1091. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/19738093
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