Memory loss and substance abuse

DEFINITION: Memory loss and its effect on other brain functions has long been associated with substance abuse, especially alcohol abuse. Memory loss is often used as an indicator of substance abuse for certain substances, such as alcohol.

Introduction

All substances of abuse have been shown to create decreased activity in the areas of the brain responsible for short-term memory and attention while the drug is being used. The lasting effects of these drugs on memory functions vary with the type of substance being abused, the amounts of substance used, and the length of time the substance was used, but generally, attention, inhibition control, working memory, and decision-making are all negatively impacted.

Substances

Different substances affect various parts of the brain and impair cognition in distinct ways. Some substances reduce the brain’s ability to focus attention, thus impairing the formation of memory. For example, amphetamine or methamphetamine affects one’s working memory (ability to hold information in the mind to use while performing complex functions), while MDMA (ecstasy) users have difficulty “coding” information (linking or associating information to be able to recall and use it later) to keep in long-term memory. Heroine's negative impact on memory may present in a way similar to dementia, which likely results in its underdiagnosis. As the cells of the hippocampus die, heroin users may experience a progressive lack of facial recognition, verbal memory, and factual recall, forgetting their address, phone number, age, who people are, and more.

One study found that MDMA use affects retrospective memory (remembering something immediately and then continuing to remember it after a short time). In this study, MDMA users were read a story, asked to immediately recall it, and then asked to recall it again after a short delay. Their ability to recall the story declined by 50 percent between the first and second time they were asked to recall it.

Those who use cocaine have impaired memory function, as do those who use cannabis (marijuana). In studies of chronic cocaine users, 57 percent of users reported significant memory problems. Genetically modified mice that were exposed to cocaine demonstrated that cocaine destroys a protein called PSD-95, which is linked to learning and long-term memory and thus is important in remembering people and places. In the mice, levels of this protein dropped 50 percent with cocaine use. Another study of amphetamine users reported that 28 percent of these users had problems with immediate and remote memory, even in younger users who had not used the drug for a long period.

Alcohol Abuse

Alcohol has been studied more extensively than many other substances concerning its use and its effects on memory loss. Even people who report drinking in smaller amounts and who are, thus, considered to be social drinkers (rather than problem drinkers) have been shown to have decreased scores on memory tests. This memory loss results from nerve cell and blood vessel damage, as well as thiamine (vitamin B1) deficiency.

Among those addicted to alcohol who enter treatment, up to 70 percent have impaired function when performing difficult memory tasks. This impaired function may only be recognizable when the person is asked to perform during tests of memory; often, people who drink alcohol have learned to function in a way that appears normal to others and possibly even to themselves. This decreased neurological function caused by alcohol is sometimes called alcohol-related brain damage (ARBD) or alcohol-related brain injury (ARBI).

Some researchers link the impaired neurologic functions of individuals with alcohol addiction, including impaired memory functions, to actual physical changes in their brains, which have shown reduced electrical activity and impaired blood flow. A disorder associated with a thiamine (vitamin B1) deficiency called Korsakoff’s psychosis, Wernicke-Korsakoff syndrome, or amnestic syndrome, affects up to 10 percent of individuals with a severe alcohol addiction. It is characterized by critical impairment in short-term memory, and those affected are unable to remember new information for more than a few seconds and are, thus, unable to retain any information for short- or long-term use.

Recovery of Memory Function

In individuals recovering from an addiction to alcohol, some memory functions have been shown to return even with no intervention, improving for some as the length of abstinence increases. In others who are recovering, memory function improves with training and practice. However, in some individuals recovering from an addiction to alcohol, only minimal function is regained.

Pharmaceutical intervention is continually investigated as a way to help affected individuals overcome addiction and regain cognitive function, including short- and long-term memory function. The focus of research includes the investigation of the role of non-coding microRNAs, enzymes involved in epigenetic changes, peroxisome proliferator-activated receptor γ (PPARγ) receptors with insulin, protein kinase Cε, vasopressin, oxytocin, and the orexigenic peptide hormone called ghrelin. However, the Food and Drug Administration (FDA) has only approved psychostimulant addiction interventions for nicotine.

Overall, memory impairment is a hallmark feature of substance abuse disorder and an obstacle in treatment for all types of substances. Those who are recovering simply do not remember what instructions they have been given to try to overcome addiction or deal with cravings for the substance. Thus, memory impairment from substance abuse undermines a user’s ability to overcome substance abuse.

Advancements in neuroscience and neuroimaging methods continue to better inform the causes, treatments, and recovery of diminished memory function related to substance abuse disorders.

Bibliography

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