 ADHD is estimated to affect about 6 – 7 % of people aged 18 and under when diagnosed via the DSM @-@ IV criteria . When diagnosed via the ICD @-@ 10 criteria rates in this age group are estimated at 1 – 2 % . Children in North America appear to have a higher rate of ADHD than children in Africa and the Middle East ; this is believed to be due to differing methods of diagnosis rather than a difference in underlying frequency . If the same diagnostic methods are used , the rates are more or less the same between countries . It is diagnosed approximately three times more often in boys than in girls . This difference between sexes may reflect either a difference in susceptibility or that females with ADHD are less likely to be diagnosed than males . 
