Attention-Deficit Hyperactivity Disorder There are many factors, which determine ADHD. This paper will show the different symptoms of ADHD and how the brain effects this disorder. It is especially difficult to establish this diagnosis in children younger than age four or five years because their characteristics behavior is much more variable than that of older children and may include features that are similar to symptoms of ADHD (First, 1994, p.81). This disorder is much more frequent in males than females by a ratio ranging from 4:1 to 9:1 depending on the setting. Usually the disorder is