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.
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).
People use drugs for many reasons—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.
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.
Find out more in chapter 1 of A quick guide to drugs and alcohol.