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Cannabis: a health perspective and research agenda



... was predominantly for religious purposes whereas in the other two regions its use was mainly recreational. Cannabis use was not perceived as a problem behaviour in the rural area given the socioreligious context of use, but it was seen as such in the urban areas where it was perceived as a deviant form of behaviour (Machado, 1994).

No survey results were available to WHO on cannabis use in any other countries from the Asian region.

4. Chemistry and pharmacology

4.1 Terminology
Cannabis is a generic term used to denote the several psychoactive preparations of the plant Cannabis sativa. The major psychoactive constituent in cannabis is D-9-tetrahydrocannabinol (THC). Compounds which are structurally similar to THC are referred to as cannabinoids. In addition, a number of recently identified compounds that differ structurally from cannabinoids nevertheless share many of their pharmacological properties. The Mexican term "marijuana" is frequently used in referring to cannabis leaves or other crude plant material in many countries. The unpollinated female plants are referred to as sinsemilla. The resin from the flowering tops of cannabis plants is called hashish. Cannabis oil (hashish oil) is a concentrate of cannabinoids obtained by solvent extraction of the crude plant material or of the resin.

4.2 Cannabis and various preparations Cannabis contains at least 60 cannabinoids, several of which are biologically active. The primary compound of interest is (-)-trans-D-9-tetrahydrocannabinol (hereafter referred to only as THC, unless otherwise specified) which is the most potent cannabinoid in the plant. Cannabinoids also occur in the plant in the form of carboxylic acid derivatives, e.g. tetrahydrocannabinolic acid. The THC content and the cannabinoid composition are known to vary widely depending upon the variety and growing conditions. The THC content in cannabis is typically in the range of 0,5 to 4 per cent (Huestis et al., 1992).

Cannabis oil, hashish and sinsemilla all contain concentrations of 7 to 14 per cent. THC content in hashish generally ranges from 2-8 per cent, although it may be as high as 10 to 20 per cent. The concentration of THC in cannabis oil varies between 15 to 50 per cent. Concerns regarding THC content in cannabis have been renewed because of recent developments in indoor hydroponic cultivation techniques. For example, these efforts have enhanced the THC content in Dutch-hemp, so-called "Netherweed", to concentrations as high as 20 per cent.

A typical joint contains between 0,5 and 1,0 g of cannabis plant matter which may vary in THC content between 5 and 150 mg (i.e. typically between 1 per cent and 15 per cent). The actual amount of THC delivered in the smoke has been estimated at 20 to 70 per cent, the rest being lost through combustion or sidestream smoke. The bioavailability of THC (the fraction of THC in the cigarette which reaches the bloodstream) from marijuana cigarettes in human subjects has been reported from 5 per cent to 24 per cent. Given all of these variables, the actual dose of THC absorbed when smoked is not easily quantified.

In general, only a small amount of cannabis (e.g. 2 to 3 mg of available THC) is required to produce a brief pleasurable high for the occasional user, and a single joint may be sufficient for two or three individuals. A heavy smoker may consume five or more joints per day, while heavy users in Jamaica, for example, may consume up to 420 mg THC per day. In clinical trials designed to assess the therapeutic potential of THC, single doses have ranged up to 20 mg in capsule form. In human experimental research, THC doses of 10, 20 and 25 mg have been administered as slow, medium and high doses.

Corrigendum : Please replace page 47 pf WHO/MSA/PSA/97.4 document to indicate Dr Harold Kalant as Chairman of the Expert Working Group.

published Friday 3 October 2003 15:35