Alcohol interferes with the ability to form new memories. As the amount of alcohol consumed increases, so does the magnitude of the memory impairments. It is like a switch goes off in the brain when a person's blood alcohol content reaches a certain level. Blackouts represent episodes of amnesia during which a subject participates in events that he/she later cannot remember. This type of amnesia is referred to as anterograde; the intoxicated individual cannot form new memories, but previous memories are not erased. A subject, who has usually consumed large quantities of alcohol rapidly, can still engage in complicated activities from holding a conversation, to driving, to dancing, to having sexual relations, etc. However, he/she may not remember all, most, or even any of his/her actions or behaviors. Recent studies indicate that blackouts are much more common among social drinkers, including college drinkers, than was previously assumed. Fragmentary blackouts (often referred to as gray-outs or brown-outs) are episodes when the drinker's memory is spotty. They may remember some things, especially if reminded by others. En bloc blackouts are stretches of time where the drinker has absolutely no memory at all. Blackouts do not involve a loss of consciousness. However, blackouts may precede passing out or losing consciousness.
The switch mentioned above is actually in a part of the brain called the hippocampus (located in the forebrain). The hippocampus plays major roles in the formation of new memories related to experienced events, accessing previous memories, and spatial navigation (which is why an intoxicated individual staggers around). Quite simply, alcohol disrupts the functioning of the hippocampus. Prolonged and chronic alcohol abuse/dependence can permanently damage the hippocampus. This is one of the first regions of the brain to be damaged in Alzheimer's disease and Alcohol Wernicke-Korsakoff Syndrome (alcohol induced dementia)
Facts: Alcohol Related Deaths
- 40% of motor vehicle fatalities (.15 BAC produces a 25-380x more likelihood to be involved in a fatal car accident)
- 60% of boating fatalities
- 70% of motorcycle fatalities
- 41% of fatal falling injuries
- 42% of death associated with fires
Suicide: Alcoholism is a factor in about 30% of all completed suicides. 7% of individuals who are alcohol dependent will take their own lives.
Alcohol Poisoning: Annually, 50 students from American universities and colleges die from alcohol poisoning, about one each weekend.
Additional: Alcohol is involved in 42% of the people treated in trauma centers.
Blood Alcohol Content
When a person consumes alcohol, it is absorbed in the stomach and small intestine. After this absorption, the alcohol enters the bloodstream by dissolving into the water of the blood. The rate of absorption depends on several factors: the concentration of the alcohol, the type of alcohol, an empty versus full stomach, and gender. Alcohol leaves the body in three ways: 5% is eliminated by the kidneys, 5% by the lungs (how breathalyzers measure alcohol levels), the rest is broken down by the liver into acetic acid. Blood alcohol content (BAC) is the concentration of alcohol in blood. It is measured as mass per volume. For example, if a person has a BAC of 0.08% it means he/she has 0.02 grams of alcohol per 100 grams of his/her blood. Generally, it takes one hour to eliminate one alcoholic drink. ("And how big was that beer sir?").
Blackouts occur after a rapid rise in blood alcohol levels. Blackouts are usually associated with a BAC 0.30% or greater. However, some people can have a blackout after one drink. At a BAC of 0.35-0.50% the person will most likely be unconscious, can slip into a coma, and may even die. Death occurs at a BAC over 0.50%.
Several other drugs are also capable of producing amnesia: Valium, Rohypnol, and GHB. Alcohol mixed with these drugs dramatically increases the likelihood of blackouts, even at lower levels of usage. THC (from marijuana) also impairs memory; using THC with alcohol will produce even greater memory impairments, including blackouts.
Alcohol and Decision Making
At a high BAC more than just memory is impaired. Alcohol effects judgment, decision-making, and impulse control. Individuals often act out of character when intoxicated, and do things that they frequently later regret. In a blackout, individuals are much more likely to engage in risky behaviors (crimes, drunk driving, fights, unprotected sex), and then have no memory of what they have done. As previously discussed, intoxicated individuals do have access to previously formed memories, including morals, ethics, rules and laws. However, they may lose the ability to base decisions on the previous stored information, or to recognize that their actions are immoral/illegal or right/wrong. They may not fully comprehend that there may be consequences for their actions, or they just don't care.
A relationship between alcohol and aggression/violence has been well established. Alcohol may not cause aggression, but it does increase the likelihood that individuals will act on their aggressive urges.
Legal Aspects of Blackouts
There is a debate related to whether an individual who commits a crime while in a blackout should be held as accountable for their actions as an individual who committed the same act while sober. The laws in most jurisdictions of the USA specifically disallow voluntary intoxication as a defense in criminal court. However, involuntary intoxication (prescribed medications, being slipped something by someone else), often is a valid defense.
Victims, who were in a blackout, represent a difficult legal challenge. For example, a woman engages in sexual activity, of which she has no memory the next day. This may be extremely out of character for her. She may assume that she was assaulted. The accused male contends that she was a willing participant or even that she initiated the sexual activity. It can be difficult, if not impossible, for another person to recognize that the individual is experiencing a blackout and will not recall these events later. How did he know that she was in a blackout and not making sound decisions? This can seriously complicate a trial in which the victim just doesn't remember what she did.
Do Blackouts Equate to Alcoholism?
Blackouts occur quite often among alcoholics. However, contrary to previous assumptions that blackouts only happen to alcoholics, it has been established that they frequently occur from social drinkers who drink too much, to the occasional binge drinker, or to an individual's one and only experience with alcohol. Black-outs are a consequence of acute intoxication regardless of age, gender, ethnicity, or if someone is alcohol dependent or not.
If excessive drinking is tolerated anywhere, it is at college campuses. A 2002 research study showed that 51% of the college students who had ever consumed alcohol reported having had a blackout.
Nonetheless, blackouts are a warning sign that an individual is drinking in dangerous and a potentially fatal manner. They should not be ignored. A person who experiences blackouts may indeed have a serious problem with alcohol. Blackouts are invariably frightening and are potentially tragic. If someone suspects that they have a problem with alcohol, a screening test is recommended. Alcohol abuse and dependence are problems that can be treated.