Water intoxication is a medical condition (also known as hyperhydration) in which an individual's intake of water is excessive. Its main consequence is hyponatremia (decreased plasma sodium, due to dilution) and suppression of the production of antidiuretic hormone. Extreme hyponatremia (with plasma sodium levels less than 100 mmol/L) frequently leads to cerebral oedema, seizures, coma, and death.
Although water intoxication invariably leads to hyponatremia, the two conditions are in fact distinct. (Hyponatremia may occur in the absence of elevated water intake; for instance in conditions such as diarrhea where excess sodium is flushed from the body).
Famous sufferers of water intoxication include Leah Betts and Anna Wood (both fatal), 2002 Boston Marathon competitor Cynthia Lucero (also fatal) and athlete Craig Barrett (recovered).
Many cases of water intoxication are related to drug use, in particular the drug MDMA (commonly referred to as ecstasy); while the media reports this as an overdose it may in fact be an idiosyncratic reaction (perhaps an unintended consequence of harm reduction advice to drink plenty of water when raving), exacerbated by hyperthermia.