Hyperactivity can be described as a state in which a person is abnormally easily excitable and exuberant. Strong emotional reactions and a very short span of attention is also typical for a hyperactive person.

Hyperactivity is sometimes associated with mania. Another, more common cause of hyperactivity is lack of sleep. More severe cases of hyperactivity can be very harmful if left untreated, since hyperactive persons seldom think about the consequences of their actions.

Hyperactivity may be related to ADHD. It has been associated with artificial food colourings such as Tartrazine.