A coma is a state of prolonged unconsciousness where a person cannot be awakened and fails to respond to stimuli. It can result from various causes, including severe head injuries, strokes, or drug overdoses. During a coma, the individual does not exhibit normal sleep-wake cycles and may require medical support for basic functions. The duration of a coma can vary significantly, ranging from a few days to several years. Recovery depends on the underlying cause and the extent of brain damage. Some individuals may regain consciousness and recover, while others may remain in a persistent vegetative state or experience severe disabilities.