Last published: November 10, 2021

What are depressants?

Depressant substances reduce arousal and stimulation. They do not necessarily make a person feel depressed. They affect the central nervous system, slowing down the messages between the brain and the body.1

They can affect concentration and coordination. They slow down a person’s ability to respond to unexpected situations. In small doses they can cause a person to feel more relaxed and less inhibited.1

In larger doses they can cause drowsiness, vomiting, unconsciousness and death.2

How are they used?

Usage depends on the specific type of depressant, for example, alcohol is drunk but benzodiazepines are usually swallowed and can also be injected. Generally, depressants can be swallowed, drunk as a beverage, injected, snorted or inhaled.

Commonly used depressants

Explore depressants on the Drug Wheel

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Effects of depressants

There is no safe level of drug use. Use of any drug always carries some risk. It’s important to be careful when taking any type of drug.

Depressants affect everyone differently, based on:

  • size, weight and health
  • whether the person is used to taking it
  • whether other drugs are taken around the same time
  • the amount taken
  • the strength of the drug (this varies from batch to batch with illegally produced drugs).

The onset and effects of depressants vary according to the type and specific chemical. Some depressants may work instantly, with effects only lasting for a short time (such as inhalants), while other depressants may take longer for the effects to start and may last longer.

In general, when small to low doses of depressants are taken, the following effects may be experienced:

  • reduced inhibitions
  • enhanced mood
  • reduced anxiety
  • slowed reaction time
  • impaired judgement
  • slowed breathing
  • increased risk of accident or injury.1

Higher doses can result in:

  • impaired judgement and coordination
  • vomiting
  • irregular or shallow breathing
  • blackouts and memory loss
  • unconsciousness
  • coma
  • death.1

Using depressants with other drugs

The effects of taking depressants with other drugs – including over-the-counter or prescribed medications – can be unpredictable and dangerous, and could cause:

More on Polydrug use

‘Polydrug use’ is a term for the use of more than one drug or type of drug at the same time or one after another.1 Polydrug use can involve both illicit drugs and legal substances, such as alcohol and medications.


Health and Safety

Use of depressants is likely to be more dangerous when:

  • combined with alcohol or other drugs, particularly
  • driving or operating heavy machinery
  • judgement or motor coordination is required
  • a person is alone (in case medical assistance is required).

Use of any drug always carries some risk, however, if you choose to take it, always try a small test amount first.4 For example, the chemical composition of GHB/GBL is highly variable. It’s very easy to take too much GHB - the difference between the amount needed to get high and the amount that causes an overdose can be hard to judge.

If drinking alcohol, stay hydrated and have something to eat before and while drinking.

Dependence and tolerance

People who use depressants regularly, can develop a dependence and tolerance to them. Tolerance means they need to take larger amounts of depressants to get the same effect.

Dependence on depressants can be psychological, physical, or both. People who are psychologically dependent may feel an urge to use them when in specific surroundings or socialising with friends. With physical dependence, a person’s body adapts to the depressants and gets used to functioning with them.

People who depend on depressants may find that using the drug becomes more important than other activities in their life. Cravings can make it difficult to stop using depressants.


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  1. Brands. B., Sproule B, & Marshman J. Drugs & Drug Abuse. 3rd ed. Ontario: Addiction Research Foundation; 1998.
  2. Australian Government Department of Health. Types of Drugs - Drug catagories: Commonwealth of Australia; 2019. [Accessed 8 February 2020].
  3. Kang M, Galuska M, Ghassemzadeh S. Benzodiazepine Toxicity. Treasure Island (FL): StatPearls Publishing; 2020.
  4. Darke S, Lappin, J. & Farrell, M. The Clinician's Guide to Illicit Drugs. United Kingdom: Silverback Publishing; 2019.