How are drugs classified?

Drugs are commonly classified according to their legal status or their effects on the central nervous system. There are three main types of drugs that affect the central nervous system:

Depressants are drugs that slow down the functions of the central nervous system. They include:

In small quantities, depressants can cause the user to feel more relaxed and less inhibited. In larger quantities, they can cause unconsciousness, vomiting and even death. Depressants affect concentration and coordination. They slow down a person's ability to respond to unexpected situations.

Stimulants act on the central nervous system to speed up the messages to and from the brain. They can make the user feel more awake, alert or confident. Stimulants increase heart rate, body temperature and blood pressure. Other effects include reduced appetite, dilated pupils, talkativeness, agitation and sleep disturbance. Mild stimulant include ephedrine used in medicines for bronchitis, hay fever and asthma, caffeine in coffee, tea and cola drinks; and nicotine in tobacco.

Stronger stimulants include:

Large quantities of stimulants can "over-stimulate" the user, causing anxiety, panic, seizures, headaches, stomach cramps, aggression and paranoia. Prolonged use of strong stimulants can mask some of the effects of depressant drugs, such as alcohol, making it difficult for a person to judge their effects.

Hallucinogens affect perception. People who have taken hallucinogens may believe they see or hear things that are not really there, or what they see may be distorted in some way. The effects of hallucinogens vary a great deal, so it is impossible to predict how they will affect a particular person at a particular time.

Cannabis is an hallucinogen as well as a depressant. Ecstasy can also have hallucinogenic qualities.

Some effects of hallucinogens include dilation of pupils, loss of appetite, emotional and psychological euphoria and wellbeing, jaw clenching, sweating, panic, paranoia, loss of contact with reality, irrational or bizarre behaviour, stomach cramps, nausea and increased activity, talking or laughing.