After a night of heavy drinking and regrets, one can experience fear and anxiety when all the memories of the previous night are nowhere to be found. Per the definition of the  National Institute on Alcohol Abuse and Alcoholism, alcohol-related blackouts are gaps in memory of events that occurred while intoxicated. Blackouts occur when a person consumes enough alcohol that it temporarily blocks the transfer of short-term to long-term memory storage in the brain region named the hippocampus. Due to the overconsumption of alcohol, memory consolidation is unable to occur. 

Blackouts are not equivalent to passing out – falling asleep or losing consciousness from alcohol consumption. During blackouts, the person is still awake but memories cannot form in the brain. Blackouts can transition to passing out depending on how much alcohol is consumed. 

In reference to the National Institute on Alcohol Abuse and Alcoholism website, there are two types of blackouts: “fragmentary blackouts” and “en bloc” blackouts. Fragmentary blackouts are when memories between events are missing and the overall recollection of the time period is spotty. En bloc blackouts are when the person is in a complete state of amnesia often for several hours. This is the most severe form of blackouts and typically in this state, memories of the events cannot be formed and usually cannot be recovered. 

Blackouts tend to occur when the blood alcohol concentration (BACs) reaches 0.16 percent or higher. At these levels of BAC, cognitive functions such as attention, judgment and decision-making are severely impaired. Because of the degree of impairment and high levels of BAC, the associated blackouts make intoxication especially more dangerous. With that being said, people can still experience blackouts at lower levels of BAC when drinking and taking sleep and anti-anxiety medications. 

According to research done at the National Institute on Alcohol Abuse and Alcoholism, blackouts are more likely to occur when alcohol enters the bloodstream too quickly, thus causing BAC levels to spike. BAC levels can increase rapidly when drinking on an empty stomach or consuming a large amount of alcohol in a short period of time. It should be noted that there are various factors to drinking and BAC levels such as gender, weight and type of drink. 

There is not enough research that covers the long term effects of heavy drinking on the brain, but there is research done at Duke University by Aaron M.White that indicates that overconsumption of alcohol damages the long term potentiation of neural signaling in the hippocampus and associated brain regions. With constant overconsumption, there are ranging levels of effects with various levels of severity: from momentary slips in memory to more permanent conditions of brain damage. Chronic alcohol consumption has been associated with damaging the frontal lobe of the brain, which controls behavior, personality, and both short and long term memory formation and recollection. With constant damage to the front lobe, the associated cognitive functions can be permanently impaired.

Blackouts are common amongst college students and other young adults, but according to College and Underage Drinking Prevention Research done by Aaron White, the frequency of blackouts is associated with alcohol-related consequences such as missing work and school, a lower grade point average and being injured. 

A blackout is not necessarily an indication of alcohol use disorder, but it is a cause for concern and should prompt people to reflect on their relationship with alcohol and consider reaching out to their healthcare providers to talk about their drinking.