Despite being the most commonly studied and diagnosed mental disorder in children the exact cause of ADHD is unknown in the majority of cases.GeneticsTwin studies, considered a key tool in behavioral genetics and other fields of study from biology to psychology, indicate that, "ADHD is often inherited from one's parents with genetics determining about 75% of cases." Genetic factors are also believed to be involved in determining whether ADHD persists into adulthood. Evolution may also play a role in higher rates of ADHD, especially hyperactive and impulsive traits, in males. Some researchers claim that these "traits" may be a form of adaptation that helps males face stressful or dangerous situations, such as quicker response to predators or superior hunting skills. A study...

According to studies published in Concise Guide to Child and Adolescent Psychiatry  although ADHD causes problems many children with ADHD have a good attention span when engaged in tasks they find interesting.Adults with ADHD are diagnosed under the same criteria as children, including having symptoms by six to twelve years of age.   Research indicates that ADHD can be difficult to distinguish from other disorders, as well as to establish what exactly is within the normal range of activity for children. Interestingly brain imaging studies do not show consistent results between individuals diagnosed with ADHD. External symptoms of hyperactivity tend to go away by young adulthood and morph into symptoms of "inner restlessness" in teens and adults with ADHD. According...