Inevitably, parents will ask themselves "What did I do to cause this?" or "How could I have prevented it?", but most of the evidence points to genetic factors, environmental facts or brain damage rather than a child's specific rearing pattern, so parents have no need to feel guilty.
Instead, parents should focus on how best to help their child with ADHD. Experts hope that someday, understanding the causes of the condition will lead to effective therapies, and evidence is building on the side of genetic causes for ADHD rather than elements of the home environment. Certain aspects of a child's environment may, however, affect the symptom severity of ADHD once it is established.
Possible causes of ADHD include
Genetics
ADHD has a strong genetic basis in the majority of cases, experts believe. It is much more common among people who have a close relative with the disorder. At the moment, researchers are investigating many different genes, particularly ones involved with the brain chemical dopamine. People with ADHD seem to have lower levels of dopamine in the brain.
Research from all over the world is collected and published by the ADHD Molecular Genetics Network. While scientific advances are allowing researchers to identify specific genes associated with ADHD, a great deal of work remains to be done.
Brain Injury
Brain injury may be a cause of attention deficit disorder. This can come about following exposure to toxins or physical injury, either before or after birth. Experts say that head injuries can cause ADHD-like symptoms in previously unaffected people, perhaps due to frontal lobe damage. Recent findings add that the extent of the ADHD symptoms is linked with the severity of the brain injury.
Nutrition and Food
Certain components of the diet, including food additives and sugar, can have clear effects on behavior. Experts believe that food additives may exacerbate ADHD, and that refined sugar may be to blame for a range of abnormal behaviors.
A scientific conference was held in 1982 to
discuss these issues. The experts concluded that
changing the diet reduced symptoms in about 5
per cent of children with ADHD. More recent
research does not show a link between ADHD and
sugar.
However, some studies suggest that a lack of
omega-3 fatty acids is linked to ADHD symptoms.
These fats are important for brain development
and function, and there is plenty of evidence
suggesting that a deficiency may contribute to
developmental disorders including ADHD. Fish oil
supplements appear to alleviate ADHD symptoms,
at least in some children, and may even boost
their performance at school.
The Environment
There may be a link between ADHD and maternal smoking. However, women who suffer from ADHD themselves are more likely to smoke, so a genetic explanation cannot be ruled out. Nevertheless, nicotine can cause hypoxia (lack of oxygen) in utero.
Lead exposure has also been suggested as a contributor to ADHD. Although paint no longer contains lead, it is possible that preschool children who live in older buildings may be exposed to toxic levels of lead from old paint or plumbing that has not been replaced.
Other Possible Causes
ADHD researchers are currently investigating the frontal lobes of the brain - the areas controlling problem-solving, planning, understanding other people's behavior, and restraining our impulses.
The brain is divided into two halves, and the two frontal lobes communicate through a bundle of nerve fibers called the corpus callosum. These areas, and nearby brain cells, are being examined by ADHD researchers. Using brain imaging methods, the experts can get an idea of the location of the psychological deficits of ADHD.
A 2002 study found that children with ADHD had 3-4 per cent smaller brain volumes in all the brain regions measured. But children on ADHD medication had similar brain volumes to unaffected children, in some of the areas measured.
One big difference was the amount of "white matter" — long-distance connections between brain regions that normally become stronger as a child grows up. Children with ADHD who had never taken medication had an abnormally small volume of white matter.
But at the moment, brain scan technology is not advanced enough to be used in ADHD diagnosis.