What is it?

Despite the large advances in understanding AD/HD, it is still, for the most part, misinterpreted. There is no single origin for the cause of AD/HD that we know of but rather a handful of biological/neurobiological, physiological and psychological theories that have been developed throughout the years.

Biological and Neurobiological Basis for AD/HD

The basis for all of the neurobiological theories is that the origin of AD/HD is hereditary. In other words, AD/HD is genetic. AD/HD is not a mental illness but rather a neurological disorder. The main reason that the symptoms of AD/HD are believed to be biological in nature is because drugs can be used to relieve many of the symptoms of AD/HD in a matter of days; if it was an environmentally induced disorder this would not be the case.

The gene that carries the AD/HD trait is believed to be autosomal dominant so

  1. If one parent has the AD/HD gene then there is a 50% chance that the child will have AD/HD.
  2. If both parents have the trait then there is a 75% to 100% chance that the child will have AD/HD.
  3. This trait does not skip generations, so if a child has AD/HD, a parent must also have it.

Neurotransmitter Deficiency

The most widely accepted of the neurobiological theories is that of a neurotransmitter deficiency, specifically that of dopamine. Medications which are used to reduce AD/HD symptoms, such as Ritalin, contain dopamine, which is good support for this neurobiological theory. The central nervous system (CNS) is the command center of the brain and contains millions of nerve cells. Each of these cells has the ability to transmit electrical impulses, much like an electrical wire, which form the foundation for thought processes. These impulses travel trough the dendrite part of the nerve cell, through the cell body, then the axon end of the cell and finally through the synapse. The synapse, which is filled with neurotransmitters, is the gap between the axon and the next adjacent nerve cell. The concentration and composition of these neurotransmitters determines how well these nerve cells communicate with each other. If these chemicals are not at correct levels, there are side effects.

The Inner Ear

The part of the brain that is affected by an inner ear problem is called the cerebral vestibular system (CVS). The CVS is the sensory processor of the brain so it takes in all sensory data, processes it and fine-tunes it. The CVS is also responsible for all motor functions and balance. An abnormality in this part of the brain can cause difficulties with coordination, energy control and the ability to focus. These symptoms are very similar to those of AD/HD so many believe that AD/HD symptoms may be a result of inner ear damage at a young age.

Hunter/Farmer Theory

Early in human evolution, it was the survival of the fittest. AD/HD symptoms make people more aware of their surroundings, more alert and better hunters. As humans evolved, this hunter trait became less and less important for survival and it began to evolve out of the gene pool. So evolution resulted in more farmers but some people, like those with AD/HD, are still hunters.

Physiological basis for ADD

Physiological factors include anything that is not inherent from birth and is caused by one’s physical surroundings. Physiological factors are not as widely accepted in the medical community as the neurobiological theories because the factual evidence supporting them is not as strong.

  • Toxins Environmental toxins such as lead have been observed to increase one’s chances of experiencing AD/HD symptoms and possibly even developing AD/HD. A study has shown that 1/3 of people with lead poisoning also show signs of AD/HD.
  • Birth complications Pregnancy and child birth complications are believed to increase the probability of having AD/HD. Any early damage to the CNS may be the cause for a small percentage of AD/HD diagnoses.
  • Sleep disorders Another theory is that AD/HD can be impacted by sleep disorders because AD/HD itself is believed by some medical professionals to be a form of a sleeping disorder. It is believed that people with AD/HD are never fully awake because they are unable to get enough sleep. Some AD/HD people may display symptoms of hyperactivity and over activity as a way to keep themselves awake.
  • Food additives Another common theory is that food additives, dyes and sugars can cause or at least increase the severity of ADD symptoms. However, it has been found that a change in one’s diet only relieves AD/HD symptoms in about 5% of patients.
  • Florescent lights There is a belief that florescent lights can make AD/HD symptoms more severe, especially hyperactivity.

Psychological basis for ADD

Psychological theories view AD/HD as a disorder based in one’s psyche. For the most part, these theories are not accepted in the medical community.


It is believed by some that environmental factors, such as parenting methods, can predict the future behavior of a child and possibly increase the severity of AD/HD symptoms. If a parent is overly controlling, neglectful or inflicts harsh punishment, their child may exhibit AD/HD symptoms.


  • Email a Friend
  • Bookmark this Page
  • Share this Page