Drugs affect the central nervous system. They do this in several ways. The socalled 'uppers' like cocaine and speed have a stimulating effect. The user feels that he has lots of energy and is much more talkative and 'loose' than usual. Heroin, alcohol and benzodiazepines, (sleeping medication and tranquillizers), on the other hand, create a mellow 'high', have a calming effect and are therefore referred to as 'downers'. Hallucinogens, such as LSD and mushrooms have a mindaltering effect: Under the influence of these, the world can look mighty different. The difference between stimulating, sedating and mind-altering substances is not always clearly defined. Some substances have a double effect. Ecstasy, for instance, stimulates and at the same time, alters the mind. Depending on the situation and the amount, cannabis can have an hallucinatory as well as a sedative effect. And of alcohol, we know that the first few glasses are stimulating but that with increasing consumption of alco the sedative effects can take over.

Apart from effects, drugs can also be categorised according to origin. LSD, Ecstasy and benzodiazepines are synthetic or semi-synthetic substances, produced in a laboratory. Hashish, cocaine, mushrooms and the opiates are derived from plants and come from natural resources. Hashish and marijuana, for instance, are derived from the plant cannabis sativa, cocaine from the coca plant, and opium, the basis of morphine, methadone and heroin, is made from the plant papaver somniferum.

The problem with urine tests

Most drugs leave metabolites behind in the urine. it is important to keep in mind that some results can produce a false negative or a false positive. Someone who has just eaten a poppy seed muffin (or any other foods containing poppy seeds) and has to take a urine test, may be accused unjustly of having used an opiate.