Q&A: The drug-induced brain and how to support those experiencing substance abuse

Some illicit substance use can have lasting neurotoxic effects, altering what our bodies consider normal function

Portrait of ASU Lecturer Shannon Eaton.

Shannon Eaton


National Substance Abuse Prevention Month, observed in October, brings awareness to substance abuse and prevention efforts.

In the past year, more than 59.3 million people age 12 or older used illicit drugs. Moreover, the use of illicit substances interferes with brain receptors and the way they process information. Once that change happens, it’s difficult to change what was altered. 

But how do drugs affect our decision-making?

Shannon Eaton, a lecturer in The College of Liberal Arts and Sciences at Arizona State University, teaches psychology and neuroscience courses at ASU Online. ASU News spoke to Eaton to learn more about the effect of drugs on the brain and how we can provide support to those who are experiencing substance abuse.

Question: Tell us about the neurological changes a person experiences when they abuse drugs.

Answer: Different drugs of abuse have many different effects. Most drugs of abuse have some interaction with the dopaminergic system — the system that is responsible for our goal-directed activities. Changes to this system can alter the desire to use drugs and make it difficult to stop.

Additionally, some drugs can cause lasting neurotoxic effects. We may see fewer neural connections, a reduced number of neurons and changes to typical neural functioning. This can impact attention, the ability to plan and the ability to make decisions.

Using drugs frequently also can result in forming associations with various drug-related cues. This learning process changes how the brain is wired and may cause increased activation of drug-related cues and environments resulting in a craving for the substance.

Q: In your course Your Brain on Drugs, you discuss how drugs influence neuron communication and human behavior. How does drug use affect that communication and human behavior? 

A: Generally we can think of our body as wanting to maintain what is “normal” for a human body. When we get too hot, we sweat to cool down and help maintain a normal temperature. Our brain acts in a similar manner. 

If we take drugs that increase signaling, our body tends to compensate by reducing the number of receptors that detect that signal, and if we take drugs that decrease signaling, our body compensates by increasing the number of receptors that detect that signal. 

Many drugs of abuse have some interaction with the parts of our brain responsible for pleasure. If we overstimulate these areas, our body will start to compensate and turn down these signals.

Q: What happens when our bodies turn down these signals?

A: The turning down of these signals makes it very difficult to stop consuming the drug. If your body compensates and reduces the number of receptors that are responsible for feeling pleasure, then something that once brought pleasure might not bring a person as much pleasure anymore.

Q: That being said, you discuss motivation and liking. What’s the difference, and how do they play a role in drug consumption?

A: We have many more parts of our brain involved in motivation and only a couple small areas that are strictly devoted to liking.  

Liking we can think of as pleasure, or hedonic value of something; the opposite would be aversion. We tend to enjoy things that bring us pleasure and will seek them out, and we tend to avoid things that are aversive. Motivation can be thought of as wanting instead of liking. It is the driving force to seek out what brings us pleasure. 

Most people start using drugs because they make them feel good, they give the user some pleasure. However, as someone continues using, their body compensates (turns down the signals) and they no longer get the same level of pleasure from using their drug — their liking decreases — but they are still highly motivated to continue use.

Many users report a decrease in liking over time but an increase in motivation to use. Many people continue to use not for the pleasure they get from the drug but because using helps them “feel normal.”

Q: Do the biological differences between men and women change the way individuals metabolize drugs? Are the neurological changes different?

A: The biological sex differences can affect how drugs are metabolized, as well as other drug effects. 

If we look at alcohol, males have more of the enzyme that metabolizes alcohol in their stomach lining. So even when controlling for body composition differences, a male will start metabolizing alcohol sooner than a female, resulting in higher blood alcohol levels in women and different subjective effects when they consume the same amount. 

Women are also more likely to experience varied subjective effects of some drugs based on their menstrual cycle. There are increased reports of drug liking prior to ovulation in women. 

When we look at differences in neural structures in individuals with substance use disorder, both males and females had less gray matter (fewer neurons) compared to controls, but the regions where these effects are observed may differ between males and females. Men tend to have more dopamine release in areas associated with reward compared to women following the administration of drugs.

Historically, both in the U.S. and worldwide, men have had higher rates of substance use and substance use disorders.

Q: You touched upon interesting research regarding prevalence rates between men and women. What do those look like now in comparison to previous years?

A: If we take alcohol as an example, approximately 100 years ago, men were three times more likely to have problematic alcohol use than women. Recently, that gender gap has been getting smaller and smaller, and now men are only about 1.2 times more likely to have problematic alcohol use, indicating that women have been increasing their use of alcohol more recently. This increase may be due to a number of different factors such as changing gender roles and delays in childbirth and child-rearing.

We also see gender differences in the progression of substance use disorder (SUD). Even though males are more likely to use and to have an SUD, females go through “telescoping” — they progress from first use to dependence and addiction at a faster pace than males.

Q: If someone has substance use disorder, what is the best way we can help or support them? 

A: I believe that individuals that have an SUD are often not treated with empathy. It can be very hard to watch someone you care about do things that we can see are hurting them and those around them. However, many people with SUD become isolated and may not have anywhere to turn when they decide it is time to get help.

  • Be there for someone who needs it. Not enabling them, but being understanding can go a long way. 

  • Not taking it personally if you reach out to help but the person isn't ready.

It is also important to keep in mind that SUDs are often a lifetime struggle. Being there for someone as they struggle can be difficult for everyone involved, but having consistency and a person they can turn to for help can be the difference in someone seeking help when they need it. 

If you or someone you know has a substance use disorder, you can contact the Substance Abuse and Mental Health Services Administration National Helpline. SAMHSA’s helpline is a free, confidential, 24/7, 365-day-a-year treatment referral and information service available in English and Spanish.

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