Unconsious person

Unconsciousness is a state which occurs when the ability to maintain an awareness of self and environment is lost. It involves a complete or near-complete lack of responsiveness to people and other environmental 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 awareness, and 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.

Unconsciousness 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, anaesthesia, and other causes.

What Causes Unconsciousness

Unconsciousness can be brought on by a major illness or injury, or complications from drug use or alcohol abuse.

Common causes of unconsciousness include:

a car accident
severe blood loss
a blow to the chest or head
a drug overdose
alcohol poisoning

A person may become temporarily unconscious (faint) when sudden changes occur within the body. Common causes of temporary unconsciousness include:

low blood sugar
low blood pressure
syncope (loss of consciousness due to lack of blood flow to the brain)
dehydration
problems with the heart’s rhythm
neurologic syncope (loss of consciousness caused by a seizure, stroke, or transient ischemic attack)
straining
hyperventilating