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ADHD

Updated 31 August 2018

Causes of ADHD

ADHD is caused by differences in neurotransmitter patterns in certain parts of the brain. ADHD has a genetic component, and a group of genes involved has been identified.

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Attention-deficit hyperactivity disorder (ADHD) is caused by differences in neurotransmitter patterns in certain parts of the brain (specifically, the cerebral cortex).

Neurotransmitters are chemicals that make it possible for nerve impulses to travel from one nerve cell to another, and therefore play an essential role in the functioning of the brain. 

The brain performs a vast range of tasks or functions, allowing us to see, hear, think, speak and move. Each function is performed by a different part of the brain. 

In individuals with ADHD, there are lower-than-normal levels of certain neurotransmitters (especially dopamine) in the regions of the brain that are responsible for regulating behaviour and attention. 

Research also confirms that the norepinephrine system is involved in some people with ADHD. Norepinephrine is another neurotransmitter found in the brain and body.

Other potential causes include:

  • Genetics: ADHD has a genetic component and a group of ADHD-related genes has been identified. The genetic component is confirmed with epidemiological studies looking at family groups. Research has shown that, in identical twins, there’s an almost 100% chance that, if one of the twins has ADHD, the other twin will show symptoms, too. In general, ADHD is genetically inherited in nearly 80% of cases.
  • Neurological damage: ADHD can also be present in some people with neurological damage occurring either before or after birth.  
  • Developmental disorders: Certain developmental disorders or syndromes, like foetal alcohol syndrome, are associated with a higher incidence of ADHD.
  • Dietary factors: Diet is often cited as the cause for ADHD, and individuals who suffer from malnutrition or who follow a nutrient-poor diet may indeed experience some of the symptoms. In a small subgroup, dietary factors (e.g. preservatives) may play a role in the worsening of symptoms (e.g. impulsivity and hyperactivity in younger children). Ongoing research is looking at the protective role that essential fatty acids may play in some people.
  • Environmental factors: Factors that may play a role in causing ADHD are low birth weight, pregnancy and birth complications, as well as smoking during pregnancy. Note that poisoning with heavy metals like lead creates a similar clinical picture in some people.
Reviewed by Prof André Venter, Head: Clinical Department of Paediatrics and Child Health, Faculty of Health Sciences at the University of the Free State. MB ChB, MMed, PhD (Canada), DCH, FCP (Paed) SA. July 2018.

Read more: 
Diagnosing ADHD

 

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ADHD Expert

Dr Renata Schoeman has been in full-time private practice as a general psychiatrist (child, adolescent and adult psychiatry) since 2008, currently based in Oude Westhof (Bellville). Renata also holds appointments as senior lecturer in Leadership (USB) and as a virtual faculty member of USB Executive Development’s Neuroleadership programme. She serves on the advisory boards of various pharmaceutical companies, as a director of the Psychiatric Management Group (PsychMG) and is the co-convenor of the South African Society of Psychiatrist (SASOP) special interest group for adult ADHD, and co-founder of the Goldilocks and The Bear Foundation (www.gb4adhd.co.za) She is passionate about corporate mental health awareness and uses her neuroscience background to assist leaders in equipping them to become balanced, healthy and dynamic leaders that take their own and their team’s emotional, intellectual, social health and physical needs into account. Renata is academically active and enjoys research and collaborative work, has published in many peer-reviewed journals, and has presented at local and international congresses. She is regularly invited to present at conferences and to engage with the media. During her post-graduate studies, she trained at Harvard, Boston in neurocognition and neuroimaging. Her awards include, amongst others, the Young Minds in Psychiatry award from the American Psychiatric Association, the Discovery Foundation Fellowship award, a Thuthuka award from the NRF, and a MRC Fellowship. She also received the Top MBA student award and the Director’s award from USB for 2015. She was a finalist for the Businesswomen’s Association of South Africa’s Businesswoman of the Year Award for 2016, and received the Excellence in Media Work award from SASOP during 2016.

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