MedlinePlus says that in the United States, about 17.6 million adults are either alcoholics or abuse alcohol. Alcoholics develop a physical dependency on alcohol, which can lead to withdrawal symptoms and memory problems. One type of memory problem associated with alcoholism is blackouts, in which the alcoholic has periods of time that he cannot remember.
Types
The National Institute on Alcohol Abuse and Alcoholism explains that two types of blackouts exist with alcoholism: en bloc blackouts and fragmentary blackouts. When a person has an en bloc blackout, she cannot remember any details of the events that occurred while she was under the influence of alcohol. Alcoholics who have en bloc blackouts can keep some information in their short-term memory for a few seconds, but they have problems taking information from their short-term memory and storing it in their long-term memory. In fragmentary blackouts, the alcoholic cannot remember certain events that occurred while under the influence of alcohol.
Blood Alcohol Concentrations
The amount of alcohol that a person consumes has an effect on whether a blackout occurs. A way to measure the amount of alcohol in a person's body is with a blood alcohol concentration, also called BAC. The University of Texas at Austin explains that if a person has a BAC of .10 percent, he has one part of alcohol per 1,000 parts of blood. The National Institute on Alcohol Abuse and Alcoholism points out that as the BAC rises, alcoholics have worse memory recall. For example, men who consumed 16 oz. to 18 oz. of 86-proof bourbon over a period four hours could not remember what they saw 30 minutes later and 24 hours later, though most could remember the information two minutes later.
Effects
The large consumption of alcohol that leads to blackouts has an effect on the brain. One area affected by alcoholism is the hippocampus, located in the temporal lobe of the brain. The hippocampus' role in memory is to take short-term memories and convert them into long-term memories, a process called consolidation. When a person consumes large amounts of alcohol, that process becomes disrupted. The National Institute on Alcohol Abuse and Alcoholism notes that when rats received alcohol, scientists found that cells in the CA1 region of the hippocampus had less activity. Blackouts from alcoholism may also result from alcohol's effects on the frontal lobes.
Genetics
Genetics may be a factor in some people having blackouts during alcohol consumption. According to Washington University in St. Louis, researchers found that a large risk for alcohol-related blackouts resulted from genetics. The researchers added that genes that may result in alcohol-related blackouts may overlap with genes linked to alcoholism.
Considerations
The National Institute on Alcohol Abuse and Alcoholism notes that up to 80 percent of alcoholics have a deficiency in thiamine, which may lead to a neurological disorder called Wernicke-Korsakoff syndrome. Patients with this disorder may develop severe memory problems, such as problems remembering new and previously learned information.
References
- MedlinePlus: Alcoholism
- National Institute on Alcohol Abuse and Alcoholism: What Happened? Alcohol, Memory Blackouts and Brain
- National Institute on Alcohol Abuse and Alcoholism: Alcohol's Damaging Effects on the Brain
- Washington University in St. Louis Newsroom: Alcohol-Induced Blackouts may be Genetic
- The University of Texas at Austin: Blood Alcohol Concentration (BAC)
