[Cannabis sativa: the plant that can induce unwanted effects and also treat them].

can be found in Chinese writings stating that, if " taken in excess, it can lead to seeing devils " , and " if taken for a long period of time, it can make people communicate with spirits " (Pen Ts'ao Ching, the earliest pharmacopeia), whereas current evidence suggests that one of the components of cannabis, cannabidiol (CBD), has antipsychotic effects. In the same direction, a number of studies show that cannabis users justify the use of the substance as a way to relax, to deal with stress, and to reduce anxiety. However, the main adverse effect of cannabis is an acute and intense anxiety reaction that often resembles panic attacks. 3 How can this plant, which is among the earliest ones cultivated by Man, induce such antagonistic effects? This question began to be answered in the first half of the 1960s by the group of Professor Raphael Mechoulam, with the discovery of the chemical structure of cannabis' major components, such as ∆ 9-tetrahidrocanabinol (∆ 9-THC), accountable for the psychoactive effects of the plant, and CBD, the best known non-psychotropic cannabinoid. Over 80 cannabinoids are known today, secreted by glands located in the head of hairs that cover the plant's flowers and leaves. The availability of these components in pure form stimulated the interest for the study of cannabis, with publications reaching their peak in the mid-1970s. In this period, a group of Brazilian researchers led by Elisaldo Luiz de Araújo Carlini made significant progress in the study of the plant, especially in regard to the interactions among cannabinoids, demonstrating that the effects of cannabis could not be fully explained by the action of ∆ 9-THC. In one of such interaction studies involving healthy volunteers, CBD was shown to attenuate the anxiety and psychotomimetic actions of elevated doses of ∆ 9-THC, suggesting that CBD could have anxiolytic and/or antipsychotic properties. That was the beginning of a line of investigation followed by our research group until today 4 and that is described in the article entitled Therapeutical use of cannabinoids in psychiatry, included in this supplement. 5 The contradictory actions of cannabinoids on mental disorders are discussed in this supplement by two other articles, one dealing with the effects of cannabinoids in psychoses and the other with the abuse of cannabis by patients with mental disorders. After the peak in the 1970s, the number of articles published in the area decreased …