It is diagnosed 4 to 9 times as frequently in boys than girls as is usually visible by that age of 3 years although the majority of children are diagnosed after they are 5 years old. The medical theory has the greatest support and the most amount of evidence to support it. Other theories are not as conclusive.
Some children have temperaments that are more feisty, difficult, or energetic.
These symptoms are disruptive to normal school routines, hence the frequency of diagnoses during the school years. This diagnoses requires that a full history and interview be made that includes parents, teachers, pediatricians, child therapists, and other specialists.