H

Hand Flapping/Hand Biting: Perseverative behaviors often seen in people with developmental disorders. These behaviors may be motivated by a sensory need, or a desire to focus and calm oneself, or to escape from a demand, or to gain access to preferred items or attention from others.

Heller's Syndrome: An alternate (older) name for Childhood Disintegrative Disorder.

High-functioning autism (HFA): A form of autism that is much less disabling as an individual has verbal ability and varying degrees of social understanding.  IQ will be measured at seventy or above.

Homeopathic: Related to homeopathy-the theory that diseases can be cured by giving very small doses of drugs that cause symptoms of the disease you are trying to cure.

Hormone: A chemical produced by an organ or gland in the body that is released into the bloodstream and affects activity elsewhere in the body.

Hyperactivity: A nervous-system-based difficulty that makes it hard for a person to control motor (muscle) behavior. It is characterized by frequent movement, rapidly switching from one activity to another, or having difficulty remaining seated or controlling restless movements.

Hyperlexia: An ability to read at an early age, but without total comprehension.

Hypersensitivity: Excessive, often painful, reaction to everyday auditory, visual, or tactile stimuli such as bright lights or loud noises.

Hyposensitivity: A marked absence of reaction to everyday stimuli.

Hypotonia: Low (reduced) muscle tone; muscles feel "floppier" than usual, and it takes more effort to initiate movement and maintain posture.