Loss of Consciousness and Fainting

Head | Neurology | Loss of Consciousness and Fainting (Symptom)


Unconsciousness is the condition of being not conscious - in a mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli. Being in a comatose state or coma is a type of unconsciousness. Fainting due to a drop in blood pressure and a decrease of the oxygen supply to the brain is a temporary loss of consciousness. Loss of consciousness must not be confused with altered states of consciousness, such as delirium (when the person is confused and only partially responsive to the environment), normal sleep, hypnosis, and other altered states in which the person responds to stimuli.

Loss of consciousness should not be confused with the notion of the psychoanalytic unconscious or cognitive processes (e. g. implicit cognition) that take place outside of awareness.


Loss of consciousness may occur as the result of traumatic brain injury, brain hypoxia (e. g. due to a brain infarction or cardiac arrest), severe poisoning with drugs that depress the activity of the central nervous system (e. g. alcohol and other hypnotic or sedative drugs), severe fatigue, and other causes.