Illegal drugs

The use of illegal drugs involves many long- and short-term risks. Do not endanger your health: do not use illegal drugs! If, however, you do in fact use illegal drugs, it is advisable to be supported or accompanied by some other person who can call the emergency services in the case of sudden severe illness.

Classification of drugs

There are different methods for classifying drugs:

  • according to legal status: legal /illegal
  • according to origin: natural, semi-synthetic and synthetic
  • according to the effect: stimulants, hallucinogens and tranquillizers.

The table below classifies the main illegal drugs according to their origin and effects.

Illegal drugs Stimulants Hallucinogens Tranquilizers
Natural Khat

Hallucinogenic mushrooms (psilocybin)

Hallucinogenic cactus (mescaline, peyote)

Salvia Divinorum (family of sage of the diviners)






LSD Heroin


MDMA, ecstasy

Ketamine, PCP



DID YOU KNOW? Drugs, whether legal or illegal, are also called “psychoactive substances”: substances which affect the brain. The adjective “psychoactive” means the same thing as “psychotropic”.

Legal and illegal drugs

Most drugs are illegal, except for coffee, tobacco, alcohol, solvents, psychotropic medications, etc.

In addition to illegal drugs, the Health Interview Survey conducted by Sciensano every 4 years also monitors and studies the consumption of these legal drugs.

Natural, semi-synthetic and synthetic drugs

  • Natural drugs are made from plants.
  • Semi-synthetic drugs are of natural origin and are subsequently modified chemically.
  • Synthetic drugs are made from chemical substances and molecules.

Stimulant, hallucinogenic, tranquillizing drugs

Drugs act on the central nervous system and alter perception, emotions and behaviour: they excite, deform reality or tranquillize.

Stimulant drugs excite a person’s psychic functions. They increase the level of alertness and general brain activity. The consumer is therefore more alert, more energetic and more euphoric. 

Hallucinogenic drugs disrupt the psychic functions. They deform the perception of reality and affect the functioning of the brain and the resulting sensations.

Tranquillizing drugs depress the psychic functions and lower the level of alertness and the general activity of the brain. They have a relaxing effect.

DID YOU KNOW? Whether they be stimulants, hallucinogens or tranquillizers, the effects of illegal drugs depend on the psychological state of the person, the context in which the drug is taken and the quantity and quality of the drug itself.

New psychoactive substances (NPSs)

NPSs, also called “legal highs”, are synthetic drugs.The chemical structure of controlled and illegal drugs is changed to create new products.

The speed with which these new substances appear on the market makes it impossible for the lawmakers to keep up with them. Therefore, they are not yet on the list of named drugs (only in French and  Dutch) which are forbidden and controlled by the law.

Because they have not yet been made illegal, NSP circulate freely on the market. Consequently, the unlicensed use and production of NPSs is not illegal. NPSs are often sold on the Internet and can cause acute poisoning (overdose), which is sometimes fatal.

Since 2005, the EU countries have notified over 450 NPSs through an European Early Warning System (European Monitoring Centre for Drugs and Drug Addiction).

Sciensano collects data and analyses the consumption of drugs, the drug market, the consequences for health, requests for treatment and the policies implemented with regard to drugs in Belgium.

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