Despite its popularity as a recreational beverage, alcohol is poisonous to many organs throughout the human body, including the brain. In some cases, people under the influence of large amounts of alcohol experience “blackouts” that produce either fragmented memory function or a complete inability to recall spans of time. In a report published in June 2014 in NIAAA Spectrum, the National Institute on Alcohol Abuse and Alcoholism (NIAAA) details the underlying causes for alcohol-related blackouts and also explains the different types of blackouts that can affect a person who drinks excessive amounts of alcohol.
Consumption of any amount of alcohol will raise your blood alcohol concentration (BAC), a measurement of how much alcohol is contained in any given volume of blood. If you drink more alcohol than your liver can safely break down and eliminate, your BAC will start to rise. In turn, increasing blood alcohol levels will have increasingly noticeable effects on your ability to function normally. Laws throughout the U.S. set a BAC of 0.08 percent as the legal determinant for driving while intoxicated. People with this amount of alcohol in their systems have clearly impaired mental functions, sensory perceptions and muscle control. These impairments are further amplified at higher blood alcohol levels, and people with a BAC of 0.15 or higher commonly experience major deficits in their ability to maintain awareness of their surroundings, control their bodies and exercise the higher-level mental functions required to do such things as follow a train of thought or make and store memories.
A person experiencing an alcohol-related blackout has typically consumed enough alcohol to seriously elevate their blood alcohol level. Apparently, in high concentrations, alcohol starts to disrupt the nerve connections inside the brain that provide basic function in the hippocampus, a brain area critical for making, storing and organizing memories, as well as for accurately recalling memories at a later point in time. In turn, this hippocampus-related memory disruption leads to blackouts, episodes of amnesia that occur while an individual remains conscious and active. Blackout episodes can vary considerably in the degree of amnesia they produce. Severely affected people can experience complete gaps in their memory that experts in the field sometimes refer to as en bloc blackouts. However, a less severely affected person may experience a “brownout” and retain spotty or partial memories of periods of heavy intoxication.
Teenagers and young adults are disproportionately impacted by alcohol-related blackouts, the NIAAA reports. Depending on the study used as source material, the number of college students who have experienced at least one such blackout ranges from roughly 10 to 25 percent. In the period of time following high school graduation, roughly 10 percent of all U.S. teenagers also experience an alcohol-related blackout. In most cases, an intoxicated person in the midst of a blackout episode gives no clear indication of the condition. In fact, affected people can basically participate in the same types of activities as their unaffected drinking counterparts. They simply have a partial or complete inability to remember what they did or said when thinking back on their actions.
While some actions taken in the midst of an alcohol blackout may be relatively harmless, others may expose an individual to increased risks for a range of severe or potentially fatal health outcomes. Examples of these highly damaging outcomes include perpetration of or exposure to physical assaults, sexual assaults or other criminal activities, involvement in motor vehicles accidents and exposure to other forms of accidental injury. The NIAAA notes that, while blacking out while drinking is not a definitive sign of diagnosable alcohol problems (alcohol abuse and/or alcoholism), people who experience blackouts need to seriously reevaluate their drinking patterns. Several factors can increase a person’s odds of experiencing a blackout while under the influence of alcohol. These factors include having experienced a blackout during one or more previous drinking bouts, drinking enough alcohol to get drunk rapidly (i.e., binge drinking), consuming alcohol without enough food in your stomach, having a genetic susceptibility to blackouts and being female. Women’s increased risks for alcohol-related blackouts stem from several underlying causes. First, women process any given amount of alcohol considerably more slowly than men, and therefore have heightened odds of experiencing blood alcohol elevations. In addition, compared to men, women have higher chances of consuming alcohol in the absence of sufficient amounts of food, as well as higher chances of consuming wine and/or liquor (two forms of alcohol substantially more potent than beer).