As with all mental disorders, the exact causes of attention deficit disorder (ADHD) are simply unknown at this time. Therefore parents should not blame themselves for this condition appearing in their child or teen. It is likely that many factors play a role in each case of a child or teen with ADHD — very little of which has to do with specific parenting or child-rearing skills.
Instead, parents should focus on how best to help their child or teen 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.
This article discusses the possible causes research has identified so far that may help explain why some children and teenagers get ADHD, while others do not. It then summarizes some of the most well-researched risk factors for ADHD.
Possible Causes of Childhood ADHD
ADHD appears to have some type of genetic basis in the majority of cases, as a child with ADHD is four times as likely to have had a relative who was also diagnosed with attention deficit 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.
A 2010 British study found one likely suspect — something called copy number variants (CNVs) in our genome. CNVs occur when there are deletions or duplications among our chromosomes (the building blocks of our DNA). The genome-wide burden of CNVs was significantly greater in ADHD patients in the study than in the controls — rates of 0.156 and 0.075, respectively.
Children with ADHD who carry a particular version of a certain gene have thinner brain tissue in the areas of the brain associated with attention. Research into this gene has showed that the difference are not permanent, however. As children with this gene grow up, their brains developed to a normal level of thickness and most ADHD symptoms subsided.
Nutrition & Food
Certain components of the diet, including food additives and sugar, appear to have clear effects on a child’s or teen’s behavior. But appearances can be deceiving.
However, the belief that sugar is one of the primary causes of attention deficit disorder does not have strong support in the research data. While some older studies did suggest a link, more recent research does not show a link between ADHD and sugar. While the jury is still out on whether sugar can contribute to ADHD symptoms, most experts now believe that the link is not a strong one. Simply removing sugar from a child’s diet is unlikely to significantly impact their ADHD behavior.
Some studies also 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.
Some experts believe that food additives may also exacerbate ADHD.
The Child or Teen’s 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.
Brain injury may also be a cause of attention deficit disorder in some very small minority of children. 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.
Risk Factors for ADHD
There are a number of things that may put a child or teen at greater risk for being diagnosed with attention deficit hyperactivity disorder. These include:
- Someone in their family (such as a brother or sister, parent, or grandparent) having ADHD or another mental disorder.
- Maternal drug use or smoking during pregnancy.
- Premature birth.
- Maternal exposure to environmental poisons — such as polychlorinated biphenyls (PCBs) — during pregnancy
- Environmental toxins, such as lead (found in peeling paint in older buildings) or being exposed to second-hand smoke.