The Biology of ADHD

MRi Brain Scans & EEG
As a Neurodevelopmental Condition, ADHD can be analysed using MRi Brain Scanning equipment and EEG (Electroencephalogram) imaging.  These specifically look at the activity of the brain in different ways which allow the electromagnetic signals to be measured and visualisations of that activity to be created.  A significant database of brain scans have been carried out during lack of activity, mental task activities, verbal activities and also day to day physical activities to provide a helpful understanding of what is taking place in the "normal/average" brain and also the "ADHD" brain.  It has become clear in these studies that the brain is a fully functional device in ADHD but is similar to "a sophisticated rocket that someone forgot to add enough fuel to".

What they have discovered is that ADHD is a condition of the Pre-Frontal Cortex (Lobe) which is not operating as it does in the wider population.  In the cases of socially problematic symptoms the sections dealing with the Executive Functions dealing with emotion suppression, inhibition and impulsivity (e.g. behavioural control) show lower activity than expected.  It is therefore understood that the executive functions are either not operating in the given situation or have operated too slowly and therefore failed to prevent the action being taken by the person with the condition.  Likewise they have discovered other areas which have increased activity and affect aspects which have not previously been considered by the diagnosis system as being symptoms of ADHD however have been noted by families and medical professionals across the globe.

The conclusion is therefore that the although fully operational the brain of an ADHD person operates in a different manner to the average population.  This causes very negative social communication and social interaction problems, and also cause or affect Learning Disabilities which in turn can again cause significant issues through out life.

Currently the problem with brain scans is the differences between each person are very very small and not noticeable by the human eye however through computer analysis of 100 subjects the computers can see very clear differences.  The change is now to develop a computerised analysis of individuals which can determine the combinations required to deem a person as having ADHD.  We wait in anticipation.

Chemical Imbalances
Due to the sometimes unusual responses of the brain they have discovered also that ADHDers also produce unusual levels of Dopamine, Cortisol and Adrenaline.

"Dopamine is mainly involved in controlling movement and aiding the flow of information to the front of the brain, which is linked to thought and emotion. It is also linked to reward systems in the brain. Problems in producing dopamine can result in Parkinson's disease, a disorder that affects a person's ability to move as they want to, resulting in stiffness, tremors or shaking, and other symptoms. Some studies suggest that having too little dopamine or problems using dopamine in the thinking and feeling regions of the brain may play a role in disorders like schizophrenia or attention deficit hyperactivity disorder (ADHD)." 
National Institute for Mental Health, USA
Cortisol, known more formally as hydrocortisone (INN, USAN, BAN), is a steroid hormone, more specifically a glucocorticoid, produced by the zona fasciculata of the adrenal cortex. It is released in response to stress and a low level of blood glucocorticoids. Its primary functions are to increase blood sugar through gluconeogenesis; suppress the immune system; and aid in fat, protein and carbohydrate metabolism. It also decreases bone formation.
The adrenal medulla is the core of the adrenal gland, and is surrounded by the adrenal cortex. It secretes approximately 20% norepinephrine (noradrenaline) and 80% epinephrine (adrenaline).[4] The chromaffin cells of the medulla, named for their characteristic brown staining with chromic acid salts, are the body's main source of the circulating catecholamines epinephrine and norepinephrine. Catecholamines are derived from the amino acid tyrosine and these water-soluble hormones are the major hormones underlying the fight-or-flight response.

This issue clearly results in a variety of problems.  Some is believed to be where the individual can portray diabetes or hyperglycaemic symptoms whilst having a fully functional system and remaining within normal sugar levels.  High adrenaline levels causes high insulin levels and combined with high cortisol levels creates a combination of an individual who is struggling with low blood sugar levels and is in a state of "fight or flight".  Significantly more research into this is needed.

Co-existing conditions such as Tourette's and OCD have problems with Glutamate levels.

Glutamate is the most common neurotransmitter, glutamate has many roles throughout the brain and nervous system. Glutamate is an excitatory transmitter: when it is released it increases the chance that the neuron will fire. This enhances the electrical flow among brain cells required for normal function and plays an important role during early brain development. It may also assist in learning and memory. Problems in making or using glutamate have been linked to many mental disorders, including autism, obsessive compulsive disorder (OCD), schizophrenia, and depression.
National Institute for Mental Health, USA

The DNA is responsible for a significant quantity of aspects of the development of the human body.  Once it was believed to contain 100% of the data that makes up a human body however this has since been proven incorrect.

The structure of DNA is a double helix (two long strands connected), which can be classified in sections called Chromosomes.  At the ends of each Chromosome are quadreplex structures (4 strands)  which allow the the cell to replicate Chromosome ends.  Overall the entire concept of DNA is rather complicated to explain but for further information go to Wikipedia.  For our purposes we need to point out that within each Chromosome are small sections which act like switches and help the body build in various ways.  Those switches consist of sections of data that appear missing, are present or are duplicated along the Chromosome double helix.  These are very small sections are are very common throughout all of the DNA.  These switches allow for things such as what colour eyes you have when the eye is constructed.

With ADHD they have found that a number of the Chromosomes lead to the size, shape and functionality of the various parts of the brain.  These variations are as common as eye colour and nose size & shapes etc and are a normal part of every human being.  Chromosomes 2, 3, 7, 15 & X are currently receiving the most study related to ADHD.  They are however also studying Chromosomes 1, 4, 8, 14, 16, 17 & 22 which are also showing clear indications of being involved as well.

Further Information
We have looked specifically at a layman's view of the issues associated with ADHD.  For a professional explanation of the normal functions of the brain please visit The National Institute of Mental Health (USA) for more in depth explanation.  Unfortunately we do not know at this time of any professional website offering a explanation of  the issues relating to ADHD and hope that this proves to be a helpful resource for everyone until such time as one is made known.

This site is intended to hold layman's explanations of the latest scientific information and is not intended to be a scientific paper.  We acknowledge some aspects of our explanations are an over simplification of the science and is based on conjecture of various leading scientists and our own knowledge.  Information on this page will change over time as a greater understanding of the science is achieved and their is greater consensus between the leading scientific minds on these issues.  We however believe we have kept as close as is possible to the best knowledge of the science and welcome any correction from those with great scientific knowledge.


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