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Causes of ADHD
What may cause ADHD?
What does NOT cause ADHD?
What may cause ADHD?
Genetic factors
There are strong indicators that ADHD or the tendency towards the disorder may be hereditary. For instance, most children with ADHD appear to have at least one blood relative with an attention disorder. At least one in three fathers who had ADHD symptoms in their youth has a child with ADHD. In addition, studies in identical twins found that there is a 91% chance that if one of the twins suffers from ADHD, the other twin will also have the condition. Research is still ongoing, but genetic factors seem to contribute to ADHD susceptibility. No single gene with major contributions to ADHD has been identified up to now.
Head injury
For a long time, many scientists believed that ADHD was the result of undetectable brain damage or minor head trauma following a serious fall, accident or difficulties during birth. As a result, ADHD used to be called “minimal brain damage” (or “minimal brain dysfunction”). Although some people with ADHD appear to have suffered certain types of head injury, the theory was rejected because it could only explain a very small number of cases. Not everyone with ADHD has a history of head trauma or brain damage.
Brain abnormalities
Researchers have discovered that, on average, children with ADHD might have up to 5 percent smaller brain volumes than children without ADHD.
Research also showed differences in some of the brain’s chemical substances that allow brain cells to communicate with one another, also called neurotransmitters. For instance, some neurotransmitters may show different activity patterns in people with ADHD compared to unaffected individuals.
Finally, studies using techniques to “image” the brain, such as the positron emission tomography (PET) scan, revealed less activity in the areas of the brain that control activity and attention in some persons with ADHD. Why this is the case in some, but not in others, remains unclear. It is important to emphasise that brain imaging techniques are currently not used to diagnose ADHD. Indeed, while these laboratory observations are consistent, they are not sufficiently sensitive to make an ADHD diagnosis.
Environmental factors
Pregnant women who smoke or use alcohol or drugs during pregnancy are at increased risk of having a child with ADHD. Pregnant women who are exposed to environmental poisons, such as polychlorinated biphenyls (PCBs - industrial chemicals that were widely used in the past), also may be more likely to have a child with symptoms of ADHD.
Preschool children exposed to certain environmental toxins, particularly lead and PCBs are at increased risk of developmental and behavioural problems, many of which are similar to those found in children diagnosed with ADHD. Exposure to lead, which is found mainly in paint and pipes in older buildings, has been linked to disruptive and even violent behaviour and to a short attention span. Exposure to PCBs in infancy may also increase a child's risk of developing ADHD.
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Diet
Many people are convinced that ADHD is caused by certain types of nutrition and that especially refined sugar and food additives can contribute to hyperactivity and attention problems. The theory that nutrition and especially junk food, sugar and additives play a role remains the topic of a much heated debate. Studies reveal that many hyperactive children do not appear to benefit from restricted diets and that these diets only seemed to help about 5% of children with ADHD and that most of these children were either very young, or suffered from food allergies. Although a healthy diet will contribute to the wellbeing of any child, including a child with ADHD, there appears to be no conclusive evidence that certain diets or food play a part in the condition.
Sleep-breathing problems
Researchers have found that children who snore are nearly twice as much at risk of being inattentive and hyperactive than those who don't. Furthermore, it was shown that snoring early in life predicted new or worsened behaviour problems four years later. Similar behaviour was seen among children who had other symptoms of sleep disturbance, such as sleep apnoea (brief breathing lapses in sleep that disrupt sleep and can reduce blood oxygen levels), or daytime sleepiness. The researchers believe that ADHD may result from the sleepiness caused by snoring. This relationship rests on the concept that snoring, sleep apnoea, and other breathing problems during sleep diminish the quality of sleep, repeatedly reduce oxygen levels, and affect daytime behaviour. This might result in an overtly tired, irritable, hyperactive child with limited attention and focus on different tasks. The researchers concluded that “these findings strengthen the hypothesis that untreated sleep-breathing problems in childhood can contribute to the development of hyperactivity”. These studies highlight the importance of diagnosing sleeping problems in children, as they can have a major impact on health, behaviour, and quality of life.
What does NOT cause ADHD?
Many people believe that ADHD is the result of a poor upbringing and bad parenting practices (or other family environment variables). This is not the case and parents should not be blamed, nor should parents feel guilty if their child suffers from ADHD. Although the condition’s causes are not fully understood, it is very clear that bad parenting does not result in ADHD.
Studies did not find a connection between watching television (or playing video games) and ADHD.
Although a lot of work remains to be done in finding the cause of ADHD, the evidence so far clearly indicates that ADHD is not the result of the home environment, but rather has biological causes. However, environmental factors may influence the severity of the disorder, and especially the degree of impairment and suffering the child may experience.
