Blackouts: Why They Happen and What They Mean

Blackouts: Why They Happen and What They Mean

Have you ever awakened only to have a blurry recollection of what transpired the night before?  Chances are, you experienced a blackout.  In the best case scenario, you only made a slight fool of yourself with friends who were also too smashed to notice, care, or remember the evening themselves.  In the worst case scenario, you may have woken up next to a stranger – or two – operated a vehicle, maxed out your credit card, or even committed a crime (Read Substance Use and Sex: Know the Risks, Drugged Driving, and When Drugs Lead to Other Problems).  Experiencing blackouts can be a sign that drinking or drug use is getting out of control.  This article will help you better gauge what you’re up against.

What is a blackout?

A blackout is a period of time that a person cannot remember; in a sense, the person has temporary amnesia. In the medical community, blackouts that occur as a result of drugs or alcohol are called “substance-induced memory impairments.”  Unlike general anesthesia, which both impairs memory and puts the patient in a sleep-like state, a person who is drunk or high may still be functional and even able to carry on a conversation during the period of time that they may not remember later.  Two types of blackouts can occur: fragmentary and en bloc.  Fragmentary blackouts are only partial blackouts; individuals who experience these may still have a general recollection of events but may not be able to recall certain parts of them.  By contrast, en bloc blackouts are complete blackouts; the person will not be able to recall any part of what they did during that period.  Although people are often able to retrospectively describe the time when an en bloc blackout began, many times, the inebriated person will fall asleep before the blackout ends.  Still, the “blackout experience” arguably falls on a continuum; someone who is even slightly tipsy may have difficulty remembering exact details of situations – like names, faces, or parts of conversations. 

Blackouts and memory

How is it possible for people to be functional in the moment yet not remember what they did later?  To answer this question, we first need a basic understanding of how memory works. According to the modal model of memory, there are three types of memory: sensory, short-term, and long-term.  Sensory memory, which lasts only a few seconds, is the most rudimentary.  Experiences that are processed in sensory memory can be passed to short-term memory, which retains information for a few minutes.  Although scholars are not certain what determines what information gets transferred into long-term memory or the mechanisms by which that occurs, they believe that rehearsal (that is, mentally repeating events in short-term memory), emotional investment, and heightened awareness may all play a role.  Most substances that can cause blackouts – including alcohol, marijuana, and benzodiazepines like Valium (diazepam) and Rohypnol (flunitrazepam) – interfere with the transition between short-term memory and long-term memory, which explains why individuals can still participate in conversations and engage in other activities (i.e., their short-term memories are still functional).  Blackouts usually do not affect previously processed long-term memories (for example, memories from childhood, etc.).

What factors contribute to the chances of having a blackout?

Again, the exact processes at work are poorly understood.  However, some research suggests that a number of factors are at play.  First, people with a history of blackouts seem to be more likely to experience blackouts, which may imply that previous substance abuse may have damaged the brain in such a way to make it more difficult for the brain to recall events that occurred during the inebriated state. One study (Weissenborn &  Duka, 2000) found that students who binge drink frequently were more likely to have trouble remembering things when drunk than students who did not engage in heavy drinking on a regular basis (Read What You and Your Young Adult Need to Know about Campus Life). Second, it may be programmed into individuals. Another study (Nelson et al., 2004) indicated that susceptibility to memory impairments from alcohol may simply be the result of an individual’s genetic makeup (Read Addiction and Genetics).  Additional research (Baer et al., 2003) tracked participants who had been exposed to alcohol while in utero for 21 years. The researchers found that those whose mothers had consumed alcohol during pregnancy were more likely to later experience blackouts and other alcohol-associated complications than those whose mothers had not (Read Alcohol & Pregnancy: A Risky Gamble and Addicted Mother, Addicted Baby: Infant Withdrawal after Birth). Third, some research (Mumenthaler et al., 1999) indicates that females may be more likely to experience a blackout even when blood alcohol level is equal – but females may be more vulnerable in general due to differences in weight, fat, and enzymes involved in metabolism. Because blackouts are partly related to blood alcohol level, drinking (or using another drug) too quickly or drinking on an empty stomach may increase your chances of a blackout. Finally, using multiple substances simultaneously can increase the chances of having a blackout.  In particular, alcohol can increase the effects of a person’s experiences with benzodiazepines, for example.

Who experiences blackouts?

Anyone can have a blackout. However, for many years, scholars believed that blackouts were only a problem among alcoholics; yet much recent research indicates that young individuals who are drinking socially may be at a particularly high risk.  A study by White et al. (2002) found that more than 50% of undergraduates had blacked out from alcohol at some point. Many of these later discovered from a friend or other source that they had engaged in risky behaviors during the period – including unprotected sex or vandalism.  As a result, some of those surveyed decided to drink less when at a social event or make other related changes to their behaviors.

What does it mean if I am having blackouts regularly?

Experiencing even a single blackout could be a sign of a developing or established addiction (Read Alcoholism: What Are the Signs? and Self-Evaluation: Is There a Problem?).  If you have had multiple blackouts in the past few months, consider speaking with your doctor, finding a rehab facility, and/or joining a 12-step program like Alcoholics or Narcotics Anonymous (Read The Whole Truth: Why You Should Be Honest with Your Doctor).

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