There are five main types of drugs that can change a person's mood or how they behave.

1. Depressants such as alcohol, can be used to calm the mind, relieve anxiety and can cause sleepiness.
2. Minor tranquillisers include the benzodiazepine drugs, such as Valium. These are often prescribed to calm people down or to help them sleep at night. They have the same general effects as depressants, but they cause addiction in a different way.
3. Opiates, also known as narcotic analgesics, are strong painkillers that produce feelings of euphoria (happiness) and sleepiness. The opiates include morphine and heroin.
4. Stimulants are drugs that make people feel more awake, alert and energetic. Stimulant drugs include cocaine and amphetamines.
5. Hallucinogens are drugs that produce strange and intense visions called hallucinations. These drugs include LSD (acid) and magic mushrooms. Many drugs don't belong to just one type. For example, cannabis can have depressant effects as well as causing euphoria, and ecstasy has both stimulant and hallucinogenic effects.