Acrophobia

from wikipedia.org:

"Acrophobia (from Greek ἄκρος, meaning "summit") is an extreme or irrational fear of heights. It is a particular case of specific phobias, which share both causes (differing in the source of the phobia) and options for treatment.

Acrophobia can be dangerous, as sufferers can experience a panic attack in a high place and become too agitated to get themselves down safely. Some acrophobics also suffer from urges to throw themselves off high places, despite not being suicidal.

This extreme fear can be counter-productive in normal everyday life though, with some sufferers being afraid to go up a flight of stairs or a ladder, or to stand on a chair, table, (etc.)."

-cliff