Psychoactive substances obtained from Cannabis sativa or Indian hemp, they are the oldest euphoriants. Also called marijuana, these substances do not usually result in physical DEPENDENCE but chronic abuse leads to passivity, apathy and inertia. Acute adverse eﬀects include transient panic reactions and toxic psychoses. The panic reactions are characterised by anxiety, helplessness and loss of control and may be accompanied by ﬂorid paranoid thoughts and hallucinations. The toxic psychoses are characterised by the sudden onset of confusion and visual hallucinations. Even at lower doses, cannabis products can precipitate functional psychoses in vulnerable individuals. The acute physical manifestations of short-term cannabis abuse are conjunctival suﬀusion and tachycardia.
The chopped leaves are usually smoked but can be eaten in food or taken as tea. The active ingredient is tetrahydrocannibol. There is much public debate in western countries over the social use of cannabis: it is illegal to possess or supply the substance in the United Kingdom, but nevertheless cannabis is quite widely used. Cannabis is classiﬁed as a Schedule 1 drug under the Misuse of Drugs Act 1971 and has not oﬃcially been used medicinally – despite some claims that it is helpful in ameliorating painful symptoms in certain serious chronic diseases such as multiple sclerosis. A related agent, NABILONE, is a synthetic cannabinoid licenced for use in treating nausea and vomiting caused by CYTOTOXIC drugs.