Substance use disorder

Substance use disorder can be caused by too much alcohol, tobacco, cannabis, hallucinogens (e.g. magic mushrooms, acid), inhalants, opioids (e.g. heroin, codeine), sedatives (e.g. benzodiazepines), stimulants (e.g. methamphetamine, cocaine) or other drugs.

Substance use disorder is the medical term for having a drug problem that affects thinking and behaviour. It involves the build-up of tolerance to the drug and symptoms of withdrawal when the drug levels in the body fall.

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

Just over one in four Australian males aged 16-85 years have substance use disorder at some point in their lives. At any one time, 4% of Australian males aged 16-85 years have substance use disorder. Substance use is twice as common in males than in females.

In addition to the criteria used to diagnose substance use disorder, there are other signs and symptoms of substance use disorder, which can be different depending on the substance. 

There are complex genetic, environmental, psychological and social causes of substance use disorder.

Substance use disorder involves changes in the ‘wiring’ of the brain, caused by substance use, that drives ongoing use of the substance. 

Not everyone who uses drugs develops substance use disorder, and some people recover while others develop greater severity.

Substance use disorder develops in:

• 16-68% of people who use nicotine
• 14-23% of people who use alcohol
• 17-21% of people who use cocaine
• 23% of people who use heroin
• 9% of people who use cannabis
• 53% of people who use meth (ice)

Personal factors such as childhood experiences, the age at which substance use begins and personality contribute to the development of substance use disorder, and are influenced by family and community support, disorder in day-to-day living, and socioeconomic disadvantage. The availability of drugs, and how they act in the body, also influences whether someone develops substance use disorder.

To diagnose substance use disorder, your doctor will ask you some questions about your substance use and your physical and mental health, and they might perform a physical examination.

There are no laboratory tests needed to diagnose substance use disorder, but your doctor might order tests to work out how much your health has been affected by your substance use, or to track progress during treatment.

Treatment for substance use disorder varies from person to person, depends on the severity of the disorder, and the substance(s) being used. Your doctor will work with you to identify the right treatment for you and track your progress. Treatments include:

• Counselling
• Self-help groups
• Medication
• Admission to hospital or a treatment facility

Counselling and medication together can be more helpful than either type of treatment alone.

In addition to treatment for substance use disorder, many people also need treatment for diseases caused by substance use. Treatment of physical or psychological health issues might be necessary.

Substance use affects many parts of the body, including the brain, heart, lungs, liver, blood and the immune and hormonal systems. There are also widespread psychological effects.

Health problems arising from substance use disorder will depend on the substance(s) being used, the amounts used and how often, and personal characteristics. Some (but not all) of the health consequences of substance use disorder are:

• Stroke
• Seizures
• Muscle weakness
• Numbness
• Memory loss
• Trouble thinking
• Personality changes
• Mood disorders
• Coma
• Death
• Heart failure
• Liver failure
• Cancer
• Infections

Substance use disorder is similar to chronic diseases like diabetes or cardiovascular disease; rather than being cured, most people experience periods of remission and relapse depending on individual circumstances. The longer someone has been in remission, the less likely there are to relapse. Remission rates for substance use disorder (from a US study) are:

• 84% for nicotine
• 91% for alcohol
• 97% for cannabis
• 99% for cocaine

For people whose substance use disorder is in remission, relapse occurs in:

• 20% (within three years) for cocaine
• More than 50% (within three years) for alcohol
• Around 50% (within one year) for nicotine

It’s best if your doctor knows about anything that might affect your health, including substance use, so you should tell them about it and answer any questions honestly.

The Alcohol and Drug Foundation can help you find services to help with substance use and provide information that’s relevant for anyone.