Want to Think Clearly? Avoid Cognitive Damage from Drug or Alcohol Abuse

Young woman pazzled

It’s ironic that the ages at which most people begin to use drugs or alcohol are the same ages that learning and development are so important. Nearly two million teens and young adults begin using alcohol and 2.4 million teens and young adults begin using marijuana every year. These are the years that should be spent learning and developing our abilities to think, come to correct conclusions, and learn job and life skills.

Learning job and life skills and coming to correct conclusions all depend on our cognitive skills. Drug and alcohol abuse is severely damaging to these abilities. A person who realizes the value of their cognitive skills would be very wise to avoid the use of drugs or the overuse of alcohol.

What Are Cognitive Skills?

They are the mental skills that enable us to be successful in the following areas:

  • Holding a job
  • Successfully getting an education
  • Maintaining healthy relationships
  • Learning new skills
  • Solving problems
  • Making rational decisions
  • Focusing our attention
  • Communicating effectively with others
  • Thinking creatively
  • Functioning in everyday life

Drugs and alcohol begin to erode these skills with the first use. Some impairment may be temporary, as when a person makes a few sketchy decisions while tipsy. Unfortunately, serious impairment can set in quickly and can be lasting. In fact, that lasting impairment can begin with the very first use. It’s not at all unusual for someone to say: “The first time I used _____, I was addicted.” Fill in that blank with heroin, methamphetamine, cocaine, crack, OxyContin, or another addictive substance.

As a person becomes addicted to any drug, their cognitive skills begin to erode quickly and may ultimately be lost completely. As proof of this loss of cognitive ability, as they continue to drink or use drugs, more and more decisions become oriented around their addiction. For example:

  • Will they be able to get a few drinks in them before meeting friends?
  • Do they have a sufficient supply of their drug of choice at home?
  • Should they skip a family event because someone might notice they are impaired?
  • Can they afford rent or food, or does their money need to go to maintaining their drug supply?
  • If they don’t have money for drugs, can they steal something of value or turn to prostitution?

Making more and more bad decisions points to a dwindling spiral of drug use and loss of life skills. Why would a person make these bad choices and then continue making them? Because drugs and alcohol lower awareness. A little bit lowers awareness a little, more lowers awareness a lot. Heavy drugs like heroin or fentanyl can eliminate awareness completely.

Addiction is defined as a compulsion to use more drugs, even when a person knows their life is being damaged by their drug use. An addicted drug user just keeps using more drugs. It’s as though the drugs themselves are doing the thinking and making the decisions.

As that compulsion sets in deeply, a person’s cognitive skills and their ability to be successful in a chosen path in life basically vanish.

Science Provides Objective Evidence of the Loss of Cognitive Ability

Writing tests

When a person becomes addicted, who notices the loss of these abilities? The individual’s parents, siblings, spouse, employer, healthcare workers, friends. The loss of these abilities tends to cause obvious problems in all areas of life, from work to relationships, from finance to education, and even to citizenship.

There is scientific research that supports this observation that drug abuse is associated with cognitive losses. One study found that drug users performed more poorly than unimpaired individuals in three measures of cognitive ability. In fact, these individuals still performed poorly on these tests three months after they abstained from drug use.

Another study that compared the impairments of individuals addicted to different drugs (marijuana, opioids, stimulants, and alcohol) found that the type of cognitive impairment varied by which drug was being used. This 2019 study also found that these impairments persisted after detoxification from drug use—even for as long as a year after abstinence began. This study also notes that cognitive losses may impact the outcome of drug treatment. If cognitive abilities are not recovered, some people may be more vulnerable to relapse.

“Cognitive alterations and deficits that are observed in substance-use disorders contribute directly and indirectly to the overall tremendous public health burden that these disorders place on society.”

Another 2019 study states: “Cognitive alterations and deficits that are observed in substance-use disorders contribute directly and indirectly to the overall tremendous public health burden that these disorders place on society.” Anyone working to try to save addicted lives witnesses these effects of cognitive deficits. It’s not a rational decision when a person overdoses, wakes up in the hospital, rips the IV out of their arm, and walks straight back to their drug dealer. But it happens far too often.

Age-Related Impacts of Drug and Alcohol Use

Young man thinking problem

There is also some evidence that in the case of marijuana, the cognitive losses are more severe when a person begins using this drug at a young age. The Substance Abuse and Mental Health Services Administration (SAMHSA) reports that adolescents who begin using marijuana before the age of 17 show more signs of cognitive loss than those who did not begin their use that early.

A 2022 report from the National Institute on Drug Abuse noted that marijuana use recently reached its highest point since 1988 among 19- to 30-year-olds. These are all-important years for completing one’s education, learning job skills, and making decisions about the future.

SAMHSA also notes that heavy alcohol use during adolescence is associated with significant cognitive impairments. The toxic effect of alcohol on the brain can magnify these negative effects.

Protecting Cognitive Ability

To a great degree, a person’s success in education, family, and work depends on their cognitive ability. When that ability is intact, they have the best chance of enjoying the kind of life they choose. When a person indulges in drug use or excessive alcohol use, they put their ability to succeed at risk.

Drug abuse and heavy alcohol use contribute to no one’s success and are much more likely to contribute to their ruin. It can be hard to convince a young person (or one who’s not so young) of this risk, but they should be warned.


  • Key Substance Use and Mental Health Indicators in the United States. Substance Abuse and Mental Health Services Administration, 2022. SAMHSA
  • Chronic drug use and cognitive impairments. ScienceDirect, 2002. ScienceDirect
  • Prevalence of cognitive impairment in patients with substance use disorder. National Library of Medicine, 2019. NLM
  • Cognitive Impairment in Substance Use Disorders. National Library of Medicine, 2019. NLM
  • Chronic Substance Use and Cognitive Effects on the Brain. Substance Abuse and Mental Health Services Administration, 2016. SAMHSA
  • Marijuana and hallucinogen use among young adults reached all time-high in 2021. National Institute on Drug Abuse, 2022. NIDA


Karen Hadley

For more than a decade, Karen has been researching and writing about drug trafficking, drug abuse, addiction and recovery. She has also studied and written about policy issues related to drug treatment.