Almost without exception, figures about how many people have a disease or abnormality are well-founded estimates. In the case of ADHD, we can only say with certainty that the percentage of children who develop the disease is the same everywhere, regardless of where they live, whether they are rich or poor, and what culture they come from. But in countries where healthcare and education are less well developed, they are less likely to be treated for the condition. In the US, the number of prescriptions written by doctors for medications to treat ADHD increased fivefold in the 1990s. This is partly because doctors are getting better at recognizing the symptoms, meaning more children are now being diagnosed, and partly because patients continue to take the drugs into adulthood.
Most figures on ADHD come from the US, but significant studies have also been conducted in other countries including Australia, Brazil, Canada, Chile, China, Germany, India, Indonesia, Israel, Netherlands, Nigeria, Puerto Rico, Thailand and The United Kingdom.
How many children have ADHD?
The estimated numbers are increasing. A safe estimate is probably four or five children in every hundred between the ages of four and fourteen (conservative estimates say three in every hundred).
Estimates vary widely, partly because the checklist of symptoms used to make the diagnosis is not the same in all countries. The estimates also vary because what doctors consider normal behavior varies. For example, what Japanese and American doctors consider a normal level of hyperactivity is seen as an exceptional level by Chinese and Indonesian doctors.
Regardless of which country or culture he or she comes from, a child has the same chance of developing ADHD.
Girls and boys
More boys are diagnosed with ADHD than girls – a lot more. The exact numbers vary, but at least three times as many boys are diagnosed as girls, and perhaps as many as six times as many. Some experts think this is partly because the condition is harder to spot in girls, who tend to be less hyperactive.
How many adults have ADHD?
The few studies that have followed children with ADHD into adulthood have shown that three quarters of patients still have the symptoms as adults. Symptoms, such as hyperactivity , become less severe with age, and those treated have learned strategies and use medications. But the condition cannot be completely cured.
