In the last decade, the number of cases of Attention Deficit Hyperactivity Disorder in children has increased by nearly 25 percent (JAMA).
Are more cases of ADHD being detected than before or are clinicians simply diagnosing ADHD more often?
Either way, one of the consequences of the rise in ADHD cases is a corresponding interest in what causes ADHD. Why do some children develop ADHD and others do not? Which factors are known to produce ADHD? Do certain parenting styles create ADHD or is it simply a matter of genetics?
Here are key facts about the causes of ADHD.
1. The vast majority of studies show that a child’s environment does not cause ADHD. Instead children are born with ADHD. It is passed along genetically, from near as well as distant relatives.
2. The main features of ADHD, including inattention, distractability, poor working memory, delayed motor development, poor emotional self-regulation, and organizational difficulty are all functions of specific areas of the brain. This suggests that neurological development plays a prime role in some children acquiring ADHD.
3. There is no credible scientific evidence that social factors, specifically the child’s home environment, directly cause ADHD.
4. Pregnancy complications are associated with increased risk for ADHD. Children whose mothers smoke and drink excessively during their pregnancy have a higher rate of ADHD. Some evidence exists that mothers who have high levels of stress and anxiety during pregnancy are also at greater risk of having children with ADHD.
5. Medication, specifically stimulant medication, is often used to treat the symptoms of ADHD. This type of medication acts to effect neurotransmitters in the brain. However, there is no evidence that these neurotransmitters themselves cause ADHD.
6. In families where at least two children have ADHD there is a 55% chance that one of the parents will also have ADHD. More distant biological relatives of children with ADHD have a 10-35% risk of having ADHD.
On the other hand, parents of adopted children who have ADHD are not any more likely to have ADHD than the general population.
These studies of parents with biological or adopted children support the conclusion that genetics play a primary role in causing ADHD.
7. Although previous research suggested that TV watching during early children contributes to ADHD more recent studies have disproved this connection.
8. There is some evidence that older types of medication used to treat seizures (phenobarbital and Dilantin) may create or intensify symptoms of ADHD.
9. Research has shown that streptococcal infections might be a contributor to some cases of ADHD. This is based on a limited number of studies, so the evidence that strep contributes to ADHD is minimal.
10. Children who have been exposed to high levels of mercury or lead are five times more likely to be identified by teachers as having problems associated with ADHD, according to recent research.
In general, the most recent studies of ADHD show that genetic and neurological factors are the probable primary causes of ADHD. Purely social factors, like parenting styles, appear to play a minor role, if any, in why children develop ADHD.