A psychoactive substance is any substance that people take to change either the way they feel, think, or behave. This includes alcohol and tobacco as well as natural and manufactured drugs. In the past, most drugs were made from plants, such as the coca bush for cocaine, opium poppies for heroin and cannabis for hashish or marijuana. Now drugs such as Ecstasy or LSD are produced by synthesizing various chemicals. Depressants are sedatives that act on the nervous system.
Stimulants are agents that activate, enhance, or increase activity of the central nervous system.
They include amphetamines and synthetic appetite suppressants such as phenmetrazine or methylphenidate. Stimulants can give rise to symptoms suggestive of intoxication, including tachycardia, pupillary dilation, elevated blood pressure and nausea or vomiting. They can also cause violent and aggressive behaviour, agitation and impaired judgement. A full-blown delusional psychosis may occur. Hallucinogens are chemically diverse and produce profound mental changes such as euphoria, anxiety, sensory distortion, vivid hallucinations, delusion, paranoia and depression.