What Causes ADHD in the Brain?

Attention-deficit/hyperactivity disorder (ADHD) is defined by difficulty in focusing along with an overabundance of energy. While ADHD typically affects children, it can also impact adults. Children who are left untreated can develop more severe symptoms that worsen in adulthood. ¹

To prevent the condition from developing, psychologists have attempted to figure out what causes ADHD in the brain. Unfortunately, we only have a vague sense of the underlying issues that develop into ADHD.

ADHD Symptoms

Since there are no accurate tests to determine ADHD, most mental health professionals look at the symptoms. ADHD symptoms vary from person to person. Not to mention, children with ADHD are likely to display different symptoms from adults with ADHD. Furthermore, there are types of ADHD, each with its own set of symptoms.

The following are the most common symptoms associated with ADHD:

• Difficulty getting along with others
• Forget or lose things
• Frequent daydreaming
• Inability to take turns
• Making careless mistakes
• Squirming or fidgeting
• Taking unnecessary risks
• Talking too much
• Trouble resisting temptation

Some of these symptoms overlap with other mental health conditions, such as anxiety and depression. For this reason, it might be difficult for a mental health professional to come to an immediate diagnosis.

What Causes ADHD?

Scientists still don’t know what causes ADHD. Research reveals there are several risk factors for individuals. These include:

• Alcohol and tobacco use during pregnancy
• Brain injury
• Exposure to environmental (i.e. lead) during pregnancy or at a young age
• Genetics
• Low birth rate
• Premature delivery

Some may assume that ADHD is the result of unhealthy activities, such as overeating sugar or watching too much television. Current research does not support these claims. However, research reveals that these behaviors can worsen symptoms of ADHD. ²

Still, rather than behavioral habits, ADHD is believed to be a product of irregularities in the brain.

The Neuroscience of ADHD

Through millions of cells (or neurons) compacted into different regions, the brain can perform many functions. From interpreting vision to helping us figure out complicated problems to regulating other organs within the body. ³

These regions are connected through myriad pathways (or neural circuits) that pass along information. For each of them to perform properly, their connections must be stimulated and maintained properly.

Research has found that those who struggle with common mental health conditions usually have a deficiency in certain neurotransmitters. This makes it difficult for information to properly transmit from one brain region to the next. ⁴

People with ADHD tend to lack the neurotransmitter known as norepinephrine. This is a key building block for our brains – starting off as dopa and then being converted into dopamine which is then converted into norepinephrine. ⁵

Norepinephrine’s responsibilities include:

• Breaking down fat
• Improving attention and focus when performing tasks
• Increasing blood pressure and blood sugar levels
• Heightening heart rate (and blood pumping from the heart)
• Memory storage
• Regulating emotions
• Sleep-wake cycle

A lack of norepinephrine has been connected to several mental health conditions. And it can play a substantial role in the development of ADHD symptoms.

ADHD Impairment in the Brain

Along with norepinephrine, ADHD will impair neurotransmitter activity in four other regions of the brain. These include:

• Basal Ganglia – All information processed within the brain is initially sent to the basal ganglia before relaying to its final destination. ADHD causes a deficiency in basal ganglia which can cause inattention and/or impulsivity. ⁶

• Frontal Cortex – With a lack of norepinephrine, this area of the brain will begin to have trouble with attention, organization, and/or executive functioning. ⁷

• Limbic System – Found deeper in the brain, this region is responsible for our emotions. A lack of maintenance can lead to inattention, restlessness, and/or emotional discomfort. ⁸

• Reticular Activating System (RAS) – Known for playing a major role in relaying transmitters among other pathways within the brain. RAS deficiency can lead to struggles with inattention, impulsivity, and/or hyperactivity. ⁹

Since these regions interact together, there needs to be stability in all four. A deficiency in one can lead to problems in another.

Final Word

While it still remains a mystery what causes ADHD in the brain, we do know those with the condition have a positive reaction to certain medications. These medications can do wonders in replacing the deficient neurotransmitters and, when combined with therapy, people can go on to live fulfilling lives.

Outside factors can also play a role in ADHD symptoms. If you’re looking for further recovery, we highly suggest researching activities and diet plans that can help ease symptoms.

References

¹ Magnus W, Nazir S, Anilkumar AC, Shaban K. Attention Deficit Hyperactivity Disorder. 2023 Aug 8. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan–. PMID: 28722868.

² Kim Y, Chang H. Correlation between attention deficit hyperactivity disorder and sugar consumption, quality of diet, and dietary behavior in school children. Nutr Res Pract. 2011 Jun;5(3):236-45. doi: 10.4162/nrp.2011.5.3.236. Epub 2011 Jun 21. PMID: 21779528; PMCID: PMC3133757.

³ Maldonado KA, Alsayouri K. Physiology, Brain. 2023 Mar 17. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan–. PMID: 31869182.

⁴ Lin SH, Lee LT, Yang YK. Serotonin and mental disorders: a concise review on molecular neuroimaging evidence. Clin Psychopharmacol Neurosci. 2014 Dec;12(3):196-202. doi: 10.9758/cpn.2014.12.3.196. Epub 2014 Dec 26. PMID: 25598822; PMCID: PMC4293164.

⁵ Vanicek T, Spies M, Rami-Mark C, Savli M, Höflich A, Kranz GS, Hahn A, Kutzelnigg A, Traub-Weidinger T, Mitterhauser M, Wadsak W, Hacker M, Volkow ND, Kasper S, Lanzenberger R. The norepinephrine transporter in attention-deficit/hyperactivity disorder investigated with positron emission tomography. JAMA Psychiatry. 2014 Dec 1;71(12):1340-1349. doi: 10.1001/jamapsychiatry.2014.1226. PMID: 25338091; PMCID: PMC4699255.

⁶ Qiu A, Crocetti D, Adler M, Mahone EM, Denckla MB, Miller MI, Mostofsky SH. Basal ganglia volume and shape in children with attention deficit hyperactivity disorder. Am J Psychiatry. 2009 Jan;166(1):74-82. doi: 10.1176/appi.ajp.2008.08030426. Epub 2008 Nov 17. PMID: 19015232; PMCID: PMC2890266.

⁷ Vaidya CJ. Neurodevelopmental abnormalities in ADHD. Curr Top Behav Neurosci. 2012;9:49-66. doi: 10.1007/7854_2011_138. PMID: 21541845; PMCID: PMC3329889.

⁸ Plessen KJ, Bansal R, Zhu H, Whiteman R, Amat J, Quackenbush GA, Martin L, Durkin K, Blair C, Royal J, Hugdahl K, Peterson BS. Hippocampus and amygdala morphology in attention-deficit/hyperactivity disorder. Arch Gen Psychiatry. 2006 Jul;63(7):795-807. doi: 10.1001/archpsyc.63.7.795. PMID: 16818869; PMCID: PMC2367150.

⁹ Bush G. Attention-deficit/hyperactivity disorder and attention networks. Neuropsychopharmacology. 2010 Jan;35(1):278-300. doi: 10.1038/npp.2009.120. PMID: 19759528; PMCID: PMC3055423.