Who gets “Blackouts” and why?

Overview

An alcoholic blackout is amnesia (memory loss) for the events of a drinking episode without loss of consciousness. Even though the important brain function of memory formation is blocked, other brain functions remain relatively intact. Therefore, during a blackout the drinker is still able to carry out conversations, drive a vehicle, and perform other tasks (although not very well). A "blackout" is not to be confused with "passing out." The blacked-out drinker is still awake and active, and may carry out complex tasks. Because of this, blackouts have been the focus of many legal cases in the criminal justice system. Criminal acts, including murder, occur and the blacked-out perpetrator later truly has no memory of committing the crime.


Blackout periods of amnesia are “anterograde,” meaning that alcohol impairs the ability to form new memories while the person is intoxicated, but does not erase memories formed before intoxication. In addition to impairing balance, motor coordination, decision-making, and many other brain functions, alcohol produces detectable memory impairments after just one or two drinks. As the amount of alcohol increases, so does the magnitude of the memory impairments. When this becomes a total block of memory formation, we call it a blackout.

Blackouts are Scary and Dangerous!

Early documentation from Alcoholics Anonymous describes a variety of blackout behaviors, including driving for long distances or carrying on apparently normal conversations. People commonly report waking in strange places with no memory of how they got there. People often engage in dangerous or harmful behaviors while blacked out... behaviors that they ordinarily wouldn't do. These include a wide range of high-risk behaviors, such as vandalism, robberies, break-ins, assault (including sexual assault), unprotected intercourse, driving an automobile, and spending money. Often significant conversations occur with undesirable outcomes that do not reflect what the person really feels or would otherwise have said.


The guilt, shame, remorse, and self-loathing that are typical after a night of drinking, especially in people who drink daily, is largely magnified by actions that are carried out while blacked out. People tend to wake up dreading finding out what they did the night before. This is especially so when people wake up in a strange place, a hospital bed, or even a jail cell with no memory of how they got there. Looking out the window to see one's car missing from the driveway with no recollection of where it ended up is a common occurrence. Getting arrested after a night of drinking for a crime committed while blacked out is a scary occurrence indeed, as the person isn't even aware of what happened, and therefore can't even provide "my side of the story." The fact that a person was blacked out does little to impress a judge in criminal court. Many people, especially those who have not experienced a blackout, do not believe it when a person says he or she cannot remember even an inkling of a conversation or event. This leads to a level of mistrust and conflict that magnifies the effect of the offending conversation or event.

Types of Blackouts

Two different types of blackouts can occur: "en bloc" and "fragmentary" blackouts. People experiencing en bloc blackouts (complete blackout) are unable to recall any events whatsoever that occurred while they were intoxicated, even when they are reminded of these events. En bloc memory impairments tend to start abruptly. We don't know when these blackouts end because people typically fall asleep before they are over. Fragmentary blackouts (partial blackout, or grey-out) involve partial blocking of memory formation for events that occurred while the person was intoxicated. People experiencing fragmentary blackouts become aware that they are missing pieces of events only after being reminded that the events occurred. However, these reminders trigger at least some recall of the initially missing information.


Fragmentary blackouts are far more common than those of the en bloc variety. The defining characteristic of a complete blackout is that memory loss is permanent and cannot be recalled under any circumstances. In fragmentary blackouts, recall is usually possible, especially if aided by cueing. Although initially the subject may be unaware that memory is missing, reminders usually help the subject remember forgotten events.

Who Gets Blackouts?

First of all, let's put to rest a commonly held myth: blackouts are no longer considered to indicate alcoholism. Anyone who drinks too much and too fast may experience a blackout, including people who seldom use alcohol. We know that the biggest factor in determining if a blackout will occur is how rapidly the blood-alcohol concentration (BAC) rises. So, anything that contributes to the BAC rising rapidly is a risk factor for a blackout. Therefore, gulping drinks, drinking on an empty stomach, or drinking liquor (opposed to beer) are risk factors for an alcoholic blackout. However, not all people who drink rapidly and excessively experience blackouts, suggesting that some people are genetically more vulnerable to alcohol blackouts. It is possible that the same genes that predispose to blackouts might also predispose to alcoholism (see "Is There an Alcoholism/Addiction Gene" Click Here).


It appears that males and females experience blackouts equally, despite the fact that (in medical studies) males drank significantly more often and more heavily than females. This outcome suggests that at any given level of alcohol consumption, females are at greater risk than males for experiencing blackouts. Research also suggests that females are more susceptible than males to milder blackouts, even when given comparable doses of alcohol. Another risk factor for blackouts is use of other drugs of abuse along with alcohol, particularly benzodiazepines (a type of sedative prescription medication), and THC (the primary psycho-active ingredient in marijuana). Benzodiazepines can cause amnesia on their own (most date-rape drugs are benzodiazepines) and alcohol enhances this effect. Similarly, the combination of alcohol and THC produces greater memory impairments than when either drug is used alone. Although blackouts themselves are not on their own indicative of alcoholism, we do know that alcoholics are more likely to experience blackouts. This is because the more prior exposure there has been to heavy drinking, the more likely a person is to blackout when intoxicated. We're not certain, but probably their prior exposure to alcohol damaged the brain in a way that predisposes them to experiencing future memory impairments.

Why do we get blackouts?

Blackouts are brought on primarily through alcohol's effects on the hippocampus, a part of the brain that is heavily involved in memory formation. Alcohol disrupts activity in the hippocampus directly, through effects on its circuitry, and indirectly, by interfering with interactions between the hippocampus and other brain regions, especially the frontal lobes, which are also involved in learning and memory formation. Chronic alcohol use damages the frontal lobes and leads to impaired performance. Shrinkage in brain volume, changes in gene expression, and disruptions in blood flow in the brain are all known to occur. This is why we are more susceptible to blackouts when we have a significant drinking history, and also one of the reasons that chronic drinkers tend to have poor memory in general (see "The Brain in Addiction and Alcoholism" Click Here).

Bottom Line

While a blackout does not on its own indicate alcoholism, it does indicate an evening of heavy and rapid drinking. Blackouts are a major cause of the problems brought on by drinking, and can be a signal that it is time to consider cutting back or stopping. Otherwise, the situation will almost certainly worsen.


To learn more about the science and psychology of addiction and recovery, and to understand why alcoholics and addicts behave the way they do, see the author's book The Alcoholic / Addict Within.
Available for sample or purchase in paperback and ebook editions at amazon.com (Click Here).  

References:
White, Aaron M. (2004). What happened? Alcohol, memory blackouts, and the brain. In U.S. National Institute on Alcohol Abuse and Alcoholism (NIAAA): Understanding the impact of alcohol on human health and well-being. Retrieved from https://pubs.niaaa.nih.gov/publications/arh27-2/186-196.html
Lee, H., Roh, S., & Kim, D. J. (2009). Alcohol-Induced Blackout. International Journal of Environmental Research and Public Health, 6(11), 2783–2792. http://doi.org/10.3390/ijerph6112783