What are drugs?

Information about drugs, the effects on people who use them and treatment options. 

Drugs are substances that change a person's physical or mental state. The vast majority of drugs are used to treat medical conditions, both physical and mental. Some, however, are used outside the medical setting for their effects on the mind. These are referred to as recreational drugs, and many of them are illegal in Australia. 

Psychoactive drugs

Drugs that affect a person's mental state, whether prescribed for a medical condition (for example, antidepressants) or taken for recreational purposes (such as alcohol and heroin), are called psychoactive drugs.

Psychoactive drugs affect the way a person thinks and feels—which may also affect the way they behave. The most commonly used legal psychoactive drugs, apart from drugs taken on prescription, are alcohol and tobacco. The most commonly used illegal psychoactive drug is cannabis (marijuana).

Categories of psychoactive drugs

Psychoactive drugs are divided into three categories (some drugs fall into more than one category):

Depressants slow down the activity of the central nervous system (the brain and spinal cord), which reduces a person's alertness, and also slows down functions such as breathing and heart rate. Examples of depressants are alcohol, heroin, cannabis, the prescription drug group of benzodiazepines and other prescription tranquilisers.

Stimulants increase the activity of the central nervous system, making the person more alert and aroused. Examples of stimulants are nicotine, caffeine, cocaine, ecstasy and the methamphetamines, speed and ice.

Hallucinogens make a person see, hear, smell or feel things that aren't there. Examples of hallucinogens are LSD, magic mushrooms, ecstasy and cannabis. 

Some drugs fall into more than one category. For example, cannabis is both a depressant and hallucinogen, while ecstasy is a stimulant and hallucinogen. 

Why do people use psychoactive drugs

People use drugs for many different reasons. These may be for fun or excitement; to feel good, better or different; to counteract negative feelings; because they are bored or curious; because their friends or family do it; or because they have a dependence on the drug. Often people who use drugs associate with other people who use drugs. It is not always clear which comes first— the friends or the drugs. 

Drug dependence

Drug dependence may occur when a person continues to use drugs — legal or illegal — even though their drug use causes them significant problems.  

It is regarded by many as a medical condition or a disorder not directly under the control of the individual. The term 'addict', with its negative implications, is no longer used. There have been recent changes to the terminology used to describe this pattern of use, with the terms alcohol/drug abuse and alcohol/drug dependence being replaced by a single term 'alcohol/drug use disorder'. However, as drug dependence is a commonly understood term, for the purposes of this website, the term dependence will be used to describe this pattern of use.

This pattern of alcohol or drug use may be diagnosed by the presence of two or more symptoms, including: 

  • a strong desire to take the drug, spending a significant amount of time obtaining the drug, using it, and/or recovering from its effect
  • difficulties in controlling its use – unsuccessful attempts to cut down or stop, or using more of the drug or using it for longer than intended
  • persisting in its use despite harmful physical or psychological consequences
  • a higher priority given to drug use than to other activities and obligations – social, recreational and work
  • the development of a tolerance to the drug
  • experiencing symptoms of withdrawal when the drug use is stopped or reduced. 


After using a drug for a while, a person may find that:

  • they need to take more of the drug to get an effect that they previously got with less, or
  • the drug simply becomes less effective in producing the desired effect.

This is called tolerance.


When a person who has been using a drug stops taking it, or reduces the dose, they may experience a physical and/or psychological reaction. This is called withdrawal. Because the person has become tolerant to the drug's effects, they have been taking the drug just to feel 'normal'.

When the drug is removed from their body, withdrawal can be very unpleasant, producing symptoms such as tremors, sweating and vomiting, as well as strong craving for the drug. For some drugs and some individuals, medical supervision during withdrawal is necessary.

The strength of the withdrawal varies, depending on: 

  • the individual person
  • the drug they have been using
  • how frequently and for how long a person has been using the drug.

Withdrawal symptoms can make it very difficult for a user to stop or reduce their drug use and it is a common reason for people to relapse into drug use.


The process by which the body eliminates a drug and its immediate physical and psychological effects is called detoxification.

Detoxification usually leads to some level of withdrawal, and withdrawal management (sometimes involving medical assistance) may be required. Anti-anxiety drugs such as benzodiazepines are sometimes prescribed for a short time during medically supervised withdrawal.

Drug treatment

A number of options for treating drug and alcohol dependence are available in Australia.

Withdrawal is only the first step towards recovering from a drug use problem. While some people are able to manage cutting down or quitting without help, access to effective treatments is crucial for many people.

A number of options for treating drug and alcohol dependence are available in Australia. Some seek to help the person achieve a drug-free lifestyle, while others recognise abstinence as one option among others. All treatments have the primary aim of minimising the harm and the risks associated with drug use.

Treatment is most effective if it is tailored to suit a person’s circumstances, and it usually involves a combination of methods:

  • for many drugs—including alcohol and tobacco—psychological interventions and good social support are important elements of recovery
  • for some drugs, there are effective medical interventions (pharmacotherapies)
  • for some drugs, there has been little or no research on effective treatments, mainly because these drugs are less widely used and have lower impact on society or they have only recently been developed.

Although in most cases a person on treatment lives in their own home during treatment, some residential programs are available. These may be appropriate for people with serious problems who have little social support. 

Psychological interventions

Three types of psychological intervention have been found effective for a broad range of drugs:

  • motivational enhancement is an approach used by the therapist to help the client to increase their motivation to decide for themselves that they really need to change their behaviour. This can help maintain commitment in people who might otherwise leave treatment before it can be effective.
  • cognitive behavioural therapy seeks to change the thoughts and ideas that lead to and maintain drug dependence, replacing them with more constructive ways of thinking. It can also be used to help a person recognise situations that place them at risk for resuming drug-taking and to reduce the anxiety often associated with stopping drug use.
  • contingency management typically uses rewards, such as vouchers, to encourage compliance with treatment and reduce drug use (voucher- based reinforcement). The vouchers are exchangeable for goods and services in the community, and clients are rewarded if they meet specific treatment goals such as drug-free urine, on-time attendance at treatment or medication compliance.

Social and family support services provide psychological support as well as helping with medical, financial, housing and legal issues, and are important in maintaining recovery in the community.


Pharmacological treatments usually involve replacing the drug with a less harmful alternative; for example, heroin may be replaced by methadone. This allows the person to regain some control over their life, and may ultimately lead to a drug-free lifestyle.

Pharmacological treatments are not available for all drugs, and even when they are available they do not work for everyone.  

Peer support programs  

Peer support programs such as Alcoholics Anonymous and Narcotics Anonymous may be helpful for people who can relate to their particular 12-step philosophical approach. There are also other peer support groups using different approaches, for example, SMART recovery® (self-management and recovery training) and Rational Recovery.

Polydrug use

Polydrug use means:

  • using two or more drugs in combination (eg tobacco and alcohol)
  • using one drug to counteract the effects (or the after effects) of another
  • using different drugs at different times over a short period of days or weeks.
  • Polydrug use is very common among people who use drugs.

Dangers of polydrug use

Using a single psychoactive drug can be dangerous; using more than one significantly increases the risks. In particular, if two drugs of the same type, such as the depressants heroin and alcohol, are used together, there are greatly increased risks of accidents, overdose and death.

Other common dangerous drug combinations include ecstasy with alcohol, heroin with sedatives, and amphetamines with sedatives.

Because alcohol is the most widely abused psychoactive drug, it is also the most commonly involved in risky polydrug use.

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