Medical explanations for blackouts include brain damage, the side effects of drugs or medications, excessive consumption of alcohol, and epileptic seizures, according to Healthgrades. Blackouts are defined as periods of time where there is a loss of memory or a loss of consciousness. People who experience blackouts are not able to recall anything about that period of time.
One type of blackout is syncope, also known as fainting, which can be caused by several circulatory conditions, including cardiac arrhythmias, postural hypotension and vasovagal syncope, according to Healthgrades. Cardiac arrhythmias are irregular heartbeats or rhythms. Postural hypotension occurs when a person faints after standing up too quickly. Vasovagal syncope occurs when there is a temporary disruption in blood flow to the brain due to neurotransmitter imbalance. Vasovagal syncope is the likely explanation when people faint because of shock or fear.
Blackouts or gaps in memory can also be caused by psychological trauma. This is known as retrograde amnesia, where people who have recently experienced trauma lose their memory of the traumatic event, according to Healthgrades.
Anyone who experiences loss of consciousness due to head injury, seizure, loss of blood or for other unexplained reasons should call 911 and seek immediate medical attention, warns Healthgrades.