Attention-deficit/hyperactivity disorder (ADHD) is a common mental health condition observed in children but also found in adults. It’s estimated that 8.4% of children and 2.5% of adults struggle with the disorder. ¹ Due to its prevalence, many ask what is the root cause of ADHD?

Unfortunately, there isn’t a singular answer. ADHD is a complicated illness that can be caused by several factors.

What is ADHD?

There are three sets of symptoms in attention-deficit/hyperactivity disorder (ADHD): ²

• Inattention – Inability to concentrate
• Hyperactivity – Excessive energy and movements
• Impulsivity – Acting on behaviors without a second thought

While some may experience both sets of symptoms, others will have either mostly inattentive or hyperactive-impulsive ones. Furthermore, mild ADHD symptoms are common among the general population. However, they become a concern when they interfere with daily responsibilities, like school and work.

ADHD treatment usually involves stimulating medication to produce attention and focus alongside a variety of psychotherapies. ³

What is the Root Cause of ADHD?

Scientists have yet to pinpoint a singular root cause of ADHD. Most people with the condition usually develop it from several sources. However, researchers aren’t even 100% sure of these sources.

It’s unclear whether or not ADHD can be avoided. Some of the factors discussed here make it so ADHD is not preventable (i.e. genetics). Still, other factors can be avoided (i.e. environmental toxins).

Brain Anatomy and Function

Researchers have pinpointed that various areas of the brain can change and lead to ADHD symptoms throughout childhood and adulthood. More particularly, these areas tend to be smaller and have more developmental difficulty. ⁴

These areas of the brain include:

• Amygdala – Involved in emotional control and prioritizing action. ⁵

• Caudate Nucleus – Responsible for decision-making and purposeful behavior. ⁶

• Cerebral Cortex – Responsible for self-management. Research has observed that children with ADHD take longer to develop this area. ⁷

• Hippocampus – Involved in long-term and working memory. ⁵

• Nucleus Accumbens – Responsible for mood, motivation, and pleasure. ⁸

Since these abnormalities work themselves out by adulthood, some believe that ADHD goes away. However, research has found ADHD can present itself in other ways, making it a lifelong condition.

Genetics

Most scientists agree that genetics plays a crucial role in the development of ADHD. In other words, if a close family member struggles with ADHD (i.e. a parent or sibling), there’s a much higher chance of a child developing it. ⁹ However, there is no ADHD gene. How ADHD passes itself through genetic lines remains in question.

Head Injuries

Since children who’ve experienced significant head injuries have developed ADHD, some scientists believe there’s a link. Still, how this link works remains unclear.

For example, some research suggests it can take well over a decade after a head injury for ADHD to develop. ¹⁰

Traumatic brain injury (TBI) may play some role in the development of ADHD or secondary ADHD. However, since research hasn’t made a clear connection, TBI doesn’t automatically result in ADHD symptoms.

Prematurity

In babies born prematurely, ADHD symptoms were more likely to develop during pre-school years. ¹¹ As reported by MedPage Today in a sibling-comparison study:

“We found that the observed association between being born premature and ADHD symptoms in childhood was not explained by genetic or environmental factors shared between siblings. In other words, the association appears to be of a causal nature.”

In such cases, children have developed more inattentive symptoms rather than hyperactive-impulsive ones. Being a mental health professional may not immediately see these symptoms, not all premature babies will find themselves with an ADHD diagnosis. ¹²

Toxins in the Environment

Since ADHD has been on the rise in recent decades, some believe it has to do with changes in the environment. More particularly, everyday toxins such as those in foods, flooring and carpeting, lawn and cleaning products, and personal-care products. ¹³

Infants and young children are most vulnerable to these toxins since their biological systems are still developing. Furthermore, research suggests that exposure to even small amounts of toxins during the fetal stages can significantly impact. ¹⁴

What Doesn’t Cause ADHD?

When it comes to the causes of ADHD, there have been some myths circulating that parents have taken seriously. We want to be clear that there’s NO evidence to suggest the following causes ADHD:

• Allergies
• Excessive sugar
• Food additives
• Immunizations

Why Do More Children Develop ADHD?

As mentioned, ADHD statistics clearly show the condition is on the rise. However, whether or not this is from a specific cause isn’t clear.

While causes like toxins in the environment or head injuries may cause this rise, there also may be more awareness. Within the past few decades, our understanding of ADHD has improved alongside our diagnosis criteria.

Since more information is available concerning this condition, more children and adults receive help who would’ve previously been unattended.

Final Word

Being that there is no specific cause of ADHD, you may never know where you or your child developed it from. However, such information isn’t necessarily important. If you know you or your child has ADHD, then you want to work on overcoming symptoms.

References

¹ Danielson ML, Bitsko RH, Ghandour RM, Holbrook JR, Kogan MD, Blumberg SJ. Prevalence of Parent-Reported ADHD Diagnosis and Associated Treatment Among U.S. Children and Adolescents, 2016. J Clin Child Adolesc Psychol. 2018 Mar-Apr;47(2):199-212. doi: 10.1080/15374416.2017.1417860. Epub 2018 Jan 24. PMID: 29363986; PMCID: PMC5834391.

² 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.

³ Nazarova VA, Sokolov AV, Chubarev VN, Tarasov VV, Schiöth HB. Treatment of ADHD: Drugs, psychological therapies, devices, complementary and alternative methods as well as the trends in clinical trials. Front Pharmacol. 2022 Nov 17;13:1066988. doi: 10.3389/fphar.2022.1066988. PMID: 36467081; PMCID: PMC9713849.

⁴ Gehricke JG, Kruggel F, Thampipop T, Alejo SD, Tatos E, Fallon J, Muftuler LT. The brain anatomy of attention-deficit/hyperactivity disorder in young adults – a magnetic resonance imaging study. PLoS One. 2017 Apr 13;12(4):e0175433. doi: 10.1371/journal.pone.0175433. PMID: 28406942; PMCID: PMC5391018.

⁵ 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.

⁶ Schrimsher GW, Billingsley RL, Jackson EF, Moore BD 3rd. Caudate nucleus volume asymmetry predicts attention-deficit hyperactivity disorder (ADHD) symptomatology in children. J Child Neurol. 2002 Dec;17(12):877-84. doi: 10.1177/08830738020170122001. PMID: 12593459.

⁷ Wolosin SM, Richardson ME, Hennessey JG, Denckla MB, Mostofsky SH. Abnormal cerebral cortex structure in children with ADHD. Hum Brain Mapp. 2009 Jan;30(1):175-84. doi: 10.1002/hbm.20496. PMID: 17985349; PMCID: PMC2883170.

⁸ Volkow ND, Wang GJ, Newcorn JH, Kollins SH, Wigal TL, Telang F, Fowler JS, Goldstein RZ, Klein N, Logan J, Wong C, Swanson JM. Motivation deficit in ADHD is associated with dysfunction of the dopamine reward pathway. Mol Psychiatry. 2011 Nov;16(11):1147-54. doi: 10.1038/mp.2010.97. Epub 2010 Sep 21. PMID: 20856250; PMCID: PMC3010326.

⁹ Thapar A, Stergiakouli E. An Overview on the Genetics of ADHD. Xin Li Xue Bao. 2008 Aug;40(10):1088-1098. doi: 10.3724/SP.J.1041.2008.01088. PMID: 20396407; PMCID: PMC2854824.

¹⁰ Narad ME, Kennelly M, Zhang N, Wade SL, Yeates KO, Taylor HG, Epstein JN, Kurowski BG. Secondary Attention-Deficit/Hyperactivity Disorder in Children and Adolescents 5 to 10 Years After Traumatic Brain Injury. JAMA Pediatr. 2018 May 1;172(5):437-443. doi: 10.1001/jamapediatrics.2017.5746. PMID: 29554197; PMCID: PMC5875309.

¹¹ Perapoch J, Vidal R, Gómez-Lumbreras A, Hermosilla E, Riera L, Cortés J, Céspedes MC, Ramos-Quiroga JA, Morros R. Prematurity and ADHD in Childhood: An Observational Register-Based Study in Catalonia. J Atten Disord. 2021 May;25(7):933-941. doi: 10.1177/1087054719864631. Epub 2019 Aug 14. PMID: 31409171.

¹² Montagna A, Karolis V, Batalle D, Counsell S, Rutherford M, Arulkumaran S, Happe F, Edwards D, Nosarti C. ADHD symptoms and their neurodevelopmental correlates in children born very preterm. PLoS One. 2020 Mar 3;15(3):e0224343. doi: 10.1371/journal.pone.0224343. PMID: 32126073; PMCID: PMC7053718.

¹³ Braun JM, Kahn RS, Froehlich T, Auinger P, Lanphear BP. Exposures to environmental toxicants and attention deficit hyperactivity disorder in U.S. children. Environ Health Perspect. 2006 Dec;114(12):1904-9. doi: 10.1289/ehp.9478. PMID: 17185283; PMCID: PMC1764142.

¹⁴ Lanphear BP. The impact of toxins on the developing brain. Annu Rev Public Health. 2015 Mar 18;36:211-30. doi: 10.1146/annurev-publhealth-031912-114413. Epub 2015 Jan 12. PMID: 25581143.