A variety of behaviors, events and conditions cause sudden memory loss, including medication use, stroke and sleep deprivation, according to WebMD. Other causes include mild head trauma, acute emotional distress and strenuous physical activity, explains Mayo Clinic.
Sudden memory loss sometimes occurs immediately following an insult to the brain, such as a severe head injury or a stroke, says WebMD. Head injuries often cause short-term and long-term memory loss, which may improve over time. Alternatively, strokes often cause only short-term memory loss, which is due to blocked blood flow or bleeding in the brain. Medications, such as antidepressants, sleeping pills and pain medicines, also frequently interfere with memory, as does a deficiency of vitamin B-12 or vitamin B-1. Excessive alcohol use also frequently causes memory loss.
Sudden episodes of memory loss that are not the result of a neurological event are sometimes the result of a condition known as transient global amnesia, Mayo Clinic explains. These episodes are generally harmless and unlikely to occur again.The exact cause of transient global amnesia is unknown. However, it often occurs following certain stressful events, such as strenuous physical activity, sexual intercourse, medical procedures, acute emotional distress, mild head trauma and sudden immersion in hot or cold water. Transient global amnesia occurs most often in people with a history of migraines, although the reason for this is unclear as of 2015.