In some cases brain tumors cause memory loss, as do conditions that interfere with blood flow and oxygen supply to parts of the brain. Senility and degenerative brain conditions such as Alzheimer's disease can affect older people's ability to remember past events. Carbon monoxide poisoning may also cause memory loss. Long-term alcohol abuse can lead to Korsakoff's syndrome, a serious disorder involving brain damage and often irreversible memory loss. Prolonged abuse of barbiturates and related drugs can bring on similar symptoms.
Severe abuse can also, it is thought, lead to delayed recall of events.
Not all causes of amnesia are preventable, but normal precautions, such as wearing a helmet while biking or a seat belt in the car, can go a long way toward preventing the serious head injuries with which amnesia is sometimes associated. Unless there is permanent brain damage, chances for recovery from amnesia are generally good.