Blackouts and Memory Loss: Causes and Consequences

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After drinking heavily over a short period of time, an unfortunate, but not uncommon, occurrence is for the drinker to “black out” or have memory loss during the period of heaviest intoxication. While it used to be thought that blackouts occurred only among alcohol-dependent persons, it is now known that many adults – and even more young adults – experience blackouts after binge drinking episodes.

What is a Blackout?

A blackout is a phenomenon caused by the intake of any substance or medication in which short-term and long-term memory creation is impaired.

According to the National Institute on Alcohol Abuse and Alcoholism (NIAA), blackouts due to alcohol intoxication are caused when excessive alcohol intake impairs information processing areas in the hippocampus, a brain region that plays a central role in the formation of new memories. In essence, memories that would normally be processed and stored are simply lost, because the brain in unable to process them.

A blackout is technically called alcohol-induced amnesia. During the period of such amnesia, a person may actively participate in events, yet have no memory or only partial memory of what occurred during that time. Some people may appear to be only mildly intoxicated and may be able to hold a conversation, while others may appear to be highly intoxicated and incoherent.

Is a Blackout Different than “Passing Out”?

There is a big difference between blacking out and passing out. When a person passes out, or loses consciousness, they are in a state similar to being asleep, and are not likely to respond to stimuli like being spoken to or touched.

When a person blacks out, they may hold conversations, make decisions and continue to drink. They appear to be conscious; yet they will not remember what happened during the time when their blood alcohol levels were excessively high. This, of course, is extremely risky, as the person may attempt to drive, have sex, or perform other risky behaviors that can lead to permanent harm and even death.

Because someone in the midst of a blackout may appear to be aware of what they are doing, it is often extremely difficult for others to recognize the experience as a blackout and possibly take appropriate action.

Kinds of Blackouts

There are two different categories of blackouts:

  • En block (complete) blackout involves total memory loss until the body’s blood alcohol level lowers and memory processing returns.
  • Partial (fragmentary) blackout means that the person may not immediately remember what happened during the blackout period, but some memories may return if certain memory cues are triggered.

Blackouts and the Link to Binge Drinking

According to the Centers for Disease Control (CDC), binge drinking is often associated with adolescents and young adults (such as high school and college students). But middle-aged and older adults are binge drinking as well.

  • About 90 percent of American adults reported binge drinking at least once.
  • The average binge is about eight drinks per occasion.
  • Binge drinking is most common among adults ages 18-34.
  • About 50% of college students report having experienced binge drinking accompanied by a blackout.

A rapid increase in blood alcohol concentration (BAC) is most consistently associated with the likelihood of a blackout. The NIAAA has defined binge drinking as the pattern of drinking that brings a person’s blood alcohol concentration to 0.08% or greater, which is the level of drunk driving. In adults, binge drinking refers to the consumption of 5 or more alcoholic drinks in a row by men and 4 or more drinks in a row by women, over a 2-hour period. Usually, a person’s BAC must reach 0.14 percent – almost twice the legal limit – to induce a blackout.

Unpredictability of Blackouts

Blackouts, while all too common, seem to have little or no identifiable pre-existing factors that trigger them (for example: time of day, emotional state before use, etc.) And while blackouts are generally associated with binge drinking, some people can consume huge amounts of alcohol without experiencing a blackout. In addition, the duration of the blackout period varies widely; it can last for minutes, hours, or days. Such unpredictability makes it more difficult to prevent and treat blackouts.


Research indicates that some users of alcohol, particularly those with a history of blackouts, are predisposed to experience blackouts more frequently. One study indicated a link between prenatal exposure to alcohol and vulnerability towards blackouts. Another study indicated a genetic predisposition towards blacking out, suggesting that some individuals may be naturally inclined to be more susceptible to the risk of experiencing alcohol-related amnesia.

Risks for Binge Drinking and Blackouts

The American Academy of Pediatrics’ Clinical Report on Binge Drinking (Sept. 2015) reported that adolescence is a critical risk period for the initiation of alcohol use, and that an early onset of drinking is associated with greater risk for later development of alcohol abuse and dependence.

The anticipated effects of alcohol ingestion, or  “alcohol expectancies,” also play a crucial role in decision-making for children and adolescents as it relates to drinking. Positive expectancies are often shaped by advertising that portrays alcohol use as a normal part of adolescent and adult social life. Other positive expectancies affect females who have a history of childhood abuse; they are more likely to endorse alcohol use as a way to reduce the ongoing tensions associated with such abuse. Youth with low coping skills are also more susceptible to peer pressure around binge drinking. College students often seek out others to drink with, and those who live in dormitories report higher drinking levels than their peers who live off campus.

Another identified risk factor for binge drinking was “drinking motives.” Drinking to enhance positive emotional states was linked to heavy drinking, and was also linked to certain personality characteristics, such as sensation seeking and impulsivity–a desire for novel experiences and a willingness to take physical and psychological risks for these experiences.

Problems Associated with Having Blackouts

Alcohol-induced blackouts are associated with the development of alcohol abuse and dependence. They are also associated with other serious problems. According to the NIAAA, repeated alcohol blackouts can cause:

  • Permanent memory impairment
  • Impaired cognitive development
  • Behavioral problems
  • Brain damage

Losing memories because of blackouts and putting yourself at risk for permanent brain and behavioral problems is extremely unwise, and more than enough reason for a rational person to avoid binge drinking.


Images Courtesy of iStock

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