A drug is any substance (with the exception of food and water) which, when taken into the body, alters the body’s function either physically and/or psychologically. Drugs may be legal (e.g. alcohol, caffeine and tobacco) or illegal (e.g. cannabis, ecstasy, cocaine and heroin).

Psychoactive drugs affect the central nervous system and alter a person’s mood, thinking and behavior.

The experience that a person has when using other drugs will be affected by their individual characteristics, the drug and the environment or place.

People use drugs for a variety of reasons. Some of the reasons people use drugs include:
- To have fun, relax, forget problems or as a form of escapism
- To gain confidence and socialize
- Out of curiosity
- To lessen inhibitions
- To remove personal responsibility for decisions
- To celebrate or commiserate
- To relieve boredom and stress
- Self-medication to cope with problems
- To fit in or feel part of a group.