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Centres for Disease Control and Prevention and The National Center on Birth Defects and Developmental Disabilities have published data on the percentage of children diagnosed with ADHD in the US between 1997 and 2018[1]. The data shows the number of children diagnosed has jumped 4.3% in the space of 21 years, making people curious; they want to know about the causes and how they can help themselves feel better. One of the theories that flooded social media in the last few years is the ADHD & dopamine deficiency theory. Let’s take a look at what studies say is the relationship between dopamine and ADHD.
What does having ADHD looks like?
Attention deficit hyperactivity disorder or in short ADHD is a condition that affects a person’s behaviour[2]. Those with ADHD, their families and their school or work environment can notice signs at an early age or later in life. The symptoms become more noticeable when circumstances of someone's life change, for example when a child is enrolled into school or when you start a new job. A study from The Center for Autism & Neurodevelopmental Disorders in California, US conducted on 72 participants showed that ADHD symptoms are associated with multiple structural changes to the brain, resulting in audio-visual, motivational, and emotional ailments[3]. People with ADHD can have difficulties with:
- falling asleep,
- getting ready on time,
- listening to and carrying out instructions,
- being organised and time management,
- focusing and completing tasks,
- coping with stress, feeling restless or impatient, and
- impulsiveness and risk-taking[2].
The brain’s motivation and reward chemical
You might have heard of dopamine before; it’s usually grouped together with serotonin, oxytocin and endorphins to form the so-called happiness chemicals. Therefore, people usually assume more dopamine equals more happiness. However, this important brain chemical has a special role in our everyday lives. All of your actions are influenced by a motive and completed to seek a reward. Dopamine has an enormous influence on your motivation and reward-seeking[4]. On one hand, dopamine is released to motivate you towards achieving your goals, and on the other dopamine is released to push you to try new things for a better reward[5,6]. Your brain also activates your dopamine system when you’re doing something you love with the people you love as it finds social interactions just as deeply rewarding as money or food[7,8,9]. For example, if you love volleyball, your body will motivate you to go and play it. Because playing volleyball is also a social interaction, dopamine will be released, you’ll feel alert, motivated and good, wanting to play volleyball soon. Dopamine also helps your body solidify the feelings and memories of relief and safety after an at-first-scary experience, rewarding you for your courage[10,11].
The building block of dopamine
For your body to be able to release dopamine, however, you need to supply it with the right building block, called l-tyrosine which is crucial for the production of dopamine in your body[12]. L-tyrosine or tyrosine for short is a compound you can find in food. Once ingested, it crosses from the blood into the brain, where it is first converted to a compound called L-DOPA, which then converts to dopamine[12]. For your body to be able to produce enough dopamine, it’s essential you provide it with an adequate amount of L-tyrosine. You can opt for protein-rich foods such as soybeans and meat or you can try out a high-quality supplement[13]. brain feed has created the world’s first natural 800mg tyrosine capsule from fermented corn which can help your body produce enough dopamine to stay alert and motivated.
More dopamine = less ADHD?
For the last decade, researchers were studying the connection between dopamine, l-tyrosine & ADHD. Reddit is full of posts on tyrosine being the go-to supplement to alleviate one’s ADHD symptoms where people talk about the effects and the l-tyrosine dosage for ADHD. Eager to show how the dopamine system decreased in action in adults with ADHD, a study was conducted on 86 participants at the Brookhaven National Laboratory (BNL), supported in part by the National Institutes of Health (NIH)[14]. They concluded that the disruption of the dopamine brain system is associated with motivation deficits in ADHD adults. While there are findings that suggest that dopamine plays a role in ADHD, more research is needed and tyrosine is not recommend as a treatment for ADHD at the present time.
Tyrosine for ADHD: the new wave of research
Since tyrosine is the building block for the motivation and reward chemical dopamine, researchers examined its role in ADHD. Researchers from the Netherlands explored the three so-called aromatic amino acids, tyrosine, phenylalanine and tryptophan in connection with ADHD in 72 children[15]. They found that a deficiency in tyrosine is unrelated to ADHD. Another study that took place in Oregon, US evaluated how dietary intake among 44 children and young adults with ADHD and 52 children and young adults without ADHD is linked to their diagnosis[16]. They found none to little variation in nutrients in both groups and therefore concluded that larger-scale studies are needed to further examine the role of tyrosine in ADHD.
There is a lack of evidence on tyrosine’s role in ADHD for now. More studies are necessary to better understand the role of nutrients and the dopamine system in ADHD. Until then, tyrosine can help healthy adults produce enough dopamine so they can feel more alert and motivated in situations in which dopamine gets released.
References
[1] ADHD Throughout the Years (2022). Centres for Disease Control and Prevention. https://www.cdc.gov/ncbddd/adhd/timeline.html
[2] Attention deficit hyperactivity disorder (ADHD) (2021). NHS. https://www.nhs.uk/conditions/attention-deficit-hyperactivity-disorder-adhd/
[3] Gehricke, J. G., Kruggel, F., Thampipop, T., Alejo, S. D., Tatos, E., Fallon, J., & Muftuler, L. T. (2017). The brain anatomy of attention-deficit/hyperactivity disorder in young adults - a magnetic resonance imaging study. PloS one, 12(4), e0175433.
[4] Mohebi, A., Pettibone, J. R., Hamid, A. A., Wong, J.-M. T., Vinson, L. T., Patriarchi, T., Tian, L., Kennedy, R. T., & Berke, J. D. (2019). Dissociable dopamine dynamics for learning and motivation. Nature, 570(7759), 65–70.
[5] Berke, J.D. (2018). What does dopamine mean? Nature Neuroscience, 21(6), 787–793.
[6] Chew, B., Hauser, T. U., Papoutsi, M., Magerkurth, J., Dolan, R. J., & Rutledge, R. B. (2019). Endogenous fluctuations in the dopaminergic midbrain drive behavioral choice variability. Proceedings of the National Academy of Sciences of the United States of America, 116(37), 18732–18737.
[7] Russo, A. M., Payet, J. M., Kent, S., Lesku, J. A., Lowry, C. A., & Hale, M. W. (2022). Acute treatment with 5-hydroxytryptophan increases social approach behaviour but does not activate serotonergic neurons in the dorsal raphe nucleus in juvenile male BALB/c mice: A model of human disorders with deficits of sociability. Journal of Psychopharmacology, 36(7), 806–818.
[8] Tomova, L., Wang, K., Thompson, T. A., Matthews, G. A., Takahashi, A., Tye, K. M., & Saxe, R. (2020). Acute social isolation evokes midbrain craving responses similar to hunger. Nature Neuroscience, 23(12), 1597–1605.
[9] Krach, S. (2010). The rewarding nature of social interactions. Frontiers in Behavioral Neuroscience, 4(22).
[10] Salinas-Hernández, X. I., Vogel, P., Betz, S., Kalisch, R., Sigurdsson, T., & Duvarci, S. (2018). Dopamine neurons drive fear extinction learning by signaling the omission of expected aversive outcomes. eLife, 7, e38818.
[11] Luo, R., Uematsu, A., Weitemier, A., Aquili, L., Koivumaa, J., McHugh, T. J., & Johansen, J. P. (2018). A dopaminergic switch for fear to safety transitions. Nature communications, 9(1), 2483.
[12] Juárez Olguín, H., Calderón Guzmán, D., Hernández García, E., & Barragán Mejía, G. (2016). The Role of Dopamine and Its Dysfunction as a Consequence of Oxidative Stress. Oxidative medicine and cellular longevity, 2016, 9730467.
[13] Nutrient Ranking Tool (n.d.). My Food Data. https://tools.myfooddata.com/nutrient-ranking-tool/Tyrosine/All/Highest/100g/Common/No
[14] Volkow, N. D., Wang, G.-J., Newcorn, J. H., Kollins, S. H., Wigal, T. L., Telang, F., Fowler, J. S., Goldstein, R. Z., Klein, N., Logan, J., Wong, C., & Swanson, J. M. (2011). Motivation deficit in ADHD is associated with dysfunction of the dopamine reward pathway. Molecular Psychiatry, 16(11), Article 11.
[15] Bergwerff, C. E., Luman, M., Blom, H. J., & Oosterlaan, J. (2016). No Tryptophan, Tyrosine and Phenylalanine Abnormalities in Children with Attention-Deficit/Hyperactivity Disorder. PloS one, 11(3), e0151100.
[16] Holton, K. F., Johnstone, J. M., Brandley, E. T., & Nigg, J. T. (2019). Evaluation of dietary intake in children and college students with and without attention-deficit/hyperactivity disorder. Nutritional neuroscience, 22(9), 664–677.
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