Today, archaeological evidence allows us to trace far in the distant past the use of psychoactive substances by human societies to bring about changes in perceptions and behaviours.

Whatever they are, and depending on the culture in which we live, these substances are familiar to us. They have always been with us. Sometimes they are a means of escaping pain or soothing anxiety, sometimes a means of pushing our limits. They all have different functions, influenced by the representation of the world developed by different cultures since the dawn of humanity.

In modern times, psychoactive substances are increasingly varied, diverse and potent. Networks distributing illegal substances are also becoming better organized and stronger, which considerably increases the availability of these drugs.

We have to deal with new epidemics of drug use, such as opiate use in North America or the explosion of Tramadol (an opiate drug) use in Africa, as well as new addictive behaviours, such as ‘non-substance’-related, behavioural addiction.