How addiction can change an individual's personality

By Tim Stoddart,
updated on Jan 20, 2023

How addiction can change an individual's personality

Have you ever seen an addiction storyline play out on television? You watch a person deteriorate from a healthy, productive member of society to a filthy criminal who only cares about himself. This isn’t always the full reality, but for many families, drastic personality changes are part of parcel of addiction

The brain experiences all pleasures in the same way. It doesn’t matter if it’s a bite of chocolate or a sip of pinot noir, the brain releases a neurotransmitter called dopamine in the nucleus accumbens, a cluster of nerve cells beneath the cerebral cortex. Scientists call this area of the brain the pleasure centre.

Addictive drugs provide a path to the pleasure centre by flooding the nucleus accumbens with dopamine. The brain quickly lays down memories of this sensation and creates a conditioned response to help get more of that pleasurable thing.

people arguing

All addictive substances affect the brain in different ways, but they all provide a powerful dopamine surge in the nucleus accumbens. Drugs that release more dopamine are considered more dangerous and addictive.

Scientists once believed that the pleasure centre alone was responsible for addiction. More recently, though, researchers discovered that dopamine plays a role in learning and memory. This is why addicts seem to become hardwired to seek drugs. Addiction trains the brain to seek drugs, and this results in some of the common behavioural changes we see in addicts.

Not everyone will end up on the streets or behind bars, but most addicts experience extreme personality and behavioral changes. The reason for the change is simple: addiction alters the brain.

So what behaviours can we look out for?


When someone is addicted, they are driven to continue abusing drugs or alcohol. If someone were to find out they were using, they may have to stop. Most addicts are also ashamed of their addictions, and they don’t want their families to know what’s really going on.

This is why almost every addict becomes secretive after they start using. They will do any and everything in their power to protect their drug abuse.


In the same way an addict keeps secrets, they may also lie to cover up their habit, or in other cases lie so that they are able to get more of what they need. For example, an addict may tell you she needs money for rent or utilities when it’s really for drugs. Even someone who was previously kind and trustworthy may surprise you with lies and manipulations. If you know someone who is struggling with addiction, be careful about taking their word at face value.

man walking in street


We all enjoy spending time with like-minded individuals. It’s fun to hang out with people who share your hobbies. But when someone becomes addicted, addiction is the only thing that

matters. Their previous life and friends challenge their newfound vice, so they’ll lock themselves away to keep the addiction private.


As evidenced by 2010 paper published in Addiction Science and Clinical Practice, drug abuse interferes with the brain’s cognitive function and how it processes memories. This is why addicts are often forgetful. In many instances, forgetfulness is one of the first signs people notice when a loved one is using.

Different substances affect memory in different ways. For example, marijuana interrupts the process of transferring short-term memories to long-term ones. And benzodiazepines interfere with the way people process memories.


People struggling with addiction are more prone to fits of anger and rage than the general population. This is especially true whenever they cannot get their hands on their substance of abuse.

A study by the National Institute on Drug Abuse’s (NIDA) Intramural Research Program (IRP) showed that mice became more aggressive when they were exposed to common human addictive behaviours.

There are a few reasons why addicts may be more prone to angry outbursts:

  • They may be suppressing unresolved trauma
  • They may be angry at themselves for their addiction and are taking it out on others
  • Someone who becomes addicted is less likely to have learned healthy anger and stress-management techniques. According to a 2008 Annals of the NY Academy of Sciences study, chronic stress is a well-known risk factor for addiction.

What to do if someone you love is addicted

If you’re seeing some of these common personality changes in someone you love, you need to address the issue before it goes any further. The longer someone remains addicted, the more difficult it may be to recover.

Start by taking the following steps:

Find proof of drug or alcohol abuse

When you confront this person, they may deny any substance abuse, which is why it’s helpful to have proof.


Have a conversation

If you care about this person, it’s important that you have a private conversation about their drug abuse. Don’t maintain high hopes for the outcome, though. Oftentimes, these conversations do not go well. The addicted person may lash out in anger when they’re confronted with their problem. Remember that your goal here is to make them aware that you know about their problem and you’re willing to help.

Stage an intervention

Interventions seem so cliché these days, but there's evidence to support this method. A 2017 cost-benefit evaluation published in the International Journal of Environmental Research and Public Health found that even brief alcohol interventions given to trauma patients were effective.

Because these confrontations can get heated, consider hiring a professional intervention expert to manage things. It helps to have someone who knows what they’re doing.

Research treatment facilities

In a best-case scenario, your loved one will be ready for treatment after the intervention. Be ready with a suggested treatment centre to help the process go smoothly. If your loved one isn’t quite ready for recovery, don’t lose hope. They know you care and will be there when they’re ready.

For more information on addicition, visit Action on Addiction.

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