Exercise-Associated Hyponatraemia is caused by one thing only: voluntary over-drinking of any fluids.
Exercise-Associated Hyponatraemia (EAH) results in water retention throughout the body. The most affected organ is the brain because the skull limits its capacity to swell. In EAH as with encephalopathy, if the brain swells too much pressure rises, first leading to loss of consciousness, usually connected to seizures, and ultimately to death from respiratory arrest.
There is no known internal biological drive that leads to over-drinking. All the evidence, then as now, shows that drinking to thirst is the only safe method during training.