What is substance use disorder?

Substance use disorder is a mental health condition that affects thinking and behaviour related to the use of a substance. People with substance use disorder develop tolerance to the substance they’re using (they need more of the drug than they did before to feel its effects) and have withdrawal symptoms when they reduce their use. The withdrawal symptoms prompt people to keep using the substance even though it’s causing them harm.


Learn more about substance use disorder on our health topic page.

How common is substance use disorder?

Substance use disorder is twice as common in males than in females. One in every four Australian males aged 16-85 years old will experience substance use disorder at some point in their lives. Substance use disorder is usually associated with tobacco, alcohol and other recreational drugs but it can also occur with some prescription medicines.

Not everyone who uses a substance develops a substance use disorder.

Substance use disorder develops in:

  • 8.9% of people who use cannabis
  • 17-20.9% of people who use cocaine
  • 14-22.7% of people who use alcohol
  • 23% of people who use heroin
  • 16-67.5% of people who use nicotine
  • 52.7% of people who use meth (ice)

What are the signs and symptoms of substance use disorder?

The criteria used by doctors to diagnose substance use disorder are:

  • Taking more of the substance, or for longer, than intended
  • Always feeling a need to cut down or control substance use, or being unsuccessful at cutting down or getting control of drug use
  • Spending a lot of time getting the substance, using it or recovering from its effects
  • An intense want or urge to use the substance
  • Repeated failures to fulfil obligations at work, school or home because of substance use
  • Continuing to use a substance even though it creates ongoing social or relationship problems, or makes them worse
  • Giving up or reducing important social, work or recreational activities because of substance use
  • Ongoing substance use in situations made physically dangerous by drug-taking
  • Using drugs even though it’s known to be causing ongoing physical or psychological problems, or making them worse
  • Development of tolerance to the drug (i.e. the same amount of the substance has less effect, or more is needed to feel the effects)
  • Withdrawal symptoms (these depend on the substance) occur after substance use. These symptoms make it likely that substance use will continue to avoid withdrawal

Signs of substance use disorder that you might notice in someone else include:

  • Increasing substance use
  • Withdrawal symptoms
  • Neglecting responsibilities
  • Avoiding friends and family
  • Lack of interest in activities that were previously enjoyed

What causes substance use disorder?

The causes of substance use disorder include combinations of genetics, personal psychological factors and environmental or social factors, including:

  • A family history of substance use disorder
  • Mental health conditions such as anxiety, depression, post-traumatic stress disorder (PTSD)
  • Using substances from a young age

Substance use disorder involves ‘rewiring’ of the brain in a way that encourages the continuation of substance use, even though the person may be aware of the damage it is causing.

Substance use disorder is not a lifestyle choice or a personality characteristic.

Many people with substance use disorder have experienced trauma.

What someone with substance use disorder might be feeling

The combination of dependence on a substance, withdrawal symptoms and changes in the brain makes it very difficult for someone with substance use disorder to stop their substance use, even though they may be aware of the damage it is causing and want to stop.

Feelings of shame and guilt can cause someone with substance use disorder to try and hide their behaviour. They might lie to support their behaviour (e.g., making up reasons for needing to borrow money) or to avoid judgement from family and friends.

People with substance use disorder may be aware that their behaviour is harming their relationships and hurting other people, and might want to make changes but are unable to do so.

What you might be feeling about someone’s substance use disorder

It can be frustrating, scary and saddening if someone you care about has substance use disorder, and it can take a lot of work to provide the support they might need to help them change their behaviour. However, close personal relationships can help people with substance use disorder to stop their substance use.

Ways that you can help someone with substance use disorder include:

  • Learning about substance use disorder, to help you understand their situation. (You’re doing it already!)
  • Reassuring them that they are valuable, and that substance use does not make them ‘bad’. It can be helpful if they know you don’t think about them in a negative way, or feel like they’re a burden.
  • Encouraging them to seek help.
  • Offering to go with them when they seek help, but respecting their boundaries and privacy. Ask for their consent before you become involved.
  • Removing access to the substance(s) that they are using.

Providing support for someone with substance use disorder is different from enabling them. Enabling behaviours include:

  • Allowing them to neglect their responsibilities
  • Giving them money or other assistance to continue using
  • Making excuses for them
  • Neglecting yourself to help them

People who support another person with substance use disorder can become codependent, meaning that they spend most of their time responding to the needs of the person with substance use disorder, to the extent that it has negative effects on their own life. Codependency is bad for both people in the relationship and can work against someone overcoming substance use disorder.

If someone who is close to you has a problem with substance use, you need to look after yourself first. You cannot help others if you are not safe and well yourself. Having someone else who can support you, while you are supporting someone with substance use disorder, can protect you from collateral damage.

The Alcohol and Drug Foundation’s Path2Help online portal can provide information to help you deal with someone else’s substance use and connect you with services that provide help for you, your loved one, and your family and friends.


Learn more about substance use disorder on our health topic page.

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