Marijuana abuse
Cannabis sativa contains over 400 compounds in addition to the psychoactive substance, delta-9-tetrahydrocannabinol (THC). Marijuana cigarettes are prepared from the leaves and flowering tops of the plant, and a typical marijuana cigarette contains 0.5 to 1 g of plant material. Although the usual THC concentration varies between 5 and 20 mg, concentrations as high as 100 mg per cigarette have been detected. Hashish is prepared from concentrated resin of Cannabis sativa and contains a THC concentration of between 8 to 12 percent by weight. “Hash oil,” a lipid-soluble plant extract, may contain a THC concentration of 25 to 60 percent, and it may be added to marijuana or hashish to enhance their THC concentration. Smoking is the most common mode of marijuana or hashish self-administration. During pyrolysis, over 150 compounds in addition to the THC are released in the smoke. Although most of these compounds do not have psychoactive properties, they do have potential physiologic effects.
THC is quickly absorbed from the lungs into blood and is then rapidly sequestered in tissues. It is metabolized primarily in the liver where it is converted to 11-hydroxy-THC, a psychoactive compound, and more than 20 other metabolites. Most THC metabolites are excreted through the feces at a rate of clearance that is relatively slow in comparison to that of most other psychoactive drugs.
Prevalance of marijuana use A 1983 National Household Survey on Drug Abuse indicated that 64 percent of young adults (aged 18
to 25) stated that they used marijuana. This represents a 59 percent increase in marijuana use over a decade; in 1972, a similar survey found that only 5 percent of young adults had tried the drug. The rate of increase in marijuana use by males appeared to have stabilized by 1985 but marijuana use among women continues to increase. A recent detailed evaluation of social and behavioral concomitants of marijuana use (published in 1984) found that young marijuana users also reported significant use of other psychoactive substances and are likely to become poly drag abusers. Survey data also report that although adolescents and young adults are aware of the potential health hazards of marijuana use, this information does not effectively deter use by many individuals.
Acute and chronic marijuana intoxication Acute intoxication from marijuana and cannabis compounds is related to both THC dose and route of administration. THC is absorbed more rapidly from marijuana smoking than from orally ingested cannabis compounds. The most frequent form of acute intoxication consists of a subjective perception of relaxation and mild euphoria resembling mild to moderate alcohol intoxication. This condition is usually accompanied by some impairment in thinking, concentration, and perceptual and psychomotor functions. Higher doses of cannabis may produce behavioral effects analogous to severe alcohol intoxication. Although the effects of acute marijuana intoxication are relatively benign in normal users, the drug can precipitate severe emotional disorders in individuals who have antecedent psychotic or neurotic problems. As with other psychoactive compounds both set (user’s expectancy) and setting (environmental context) are important determinants of the type and severity of behavioral intoxication.
As is true of alcoholics, chronic marijuana abusers may lose interest in common socially desirable goals and devote progressively more time to drug acquisition and use. However, it should be emphasized that THC does not cause a specific and unique “amoti-vational syndrome.” The range of symptoms sometimes attributed to marijuana use are difficult to distinguish from mild depression and the maturational dysfunctions often associated with protracted adolescence. Chronic use of marijuana has also been reported to increase the probability of exacerbation of psychotic symptoms in individuals with a past history of schizophrenia.
Physical effects of marijuana Conjunctival injection and tachycardia are the most frequent immediate physical concomitants of smoking marijuana. Tolerance for marijuana-induced tachycardia develops rapidly among regular users; angina may be precipitated by marijuana smoking in persons with a history of coronary insufficiency. Exercise-induced angina may be increased after marijuana use to a greater extent than after tobacco cigarette smoking. Patients with cardiac disease should be strongly advised not to smoke marijuana or use cannabis compounds.
Significant decrements in pulmonary vital capacity have been found in regular daily marijuana smokers. Because marijuana smoking typically involves deep inhalation and prolonged retention of marijuana smoke, marijuana smokers may develop pulmonary disease such as chronic bronchial irritation. Impairment of single-breath carbon monoxide diffusion capacity (DLCO) is greater in persons who smoke both marijuana and tobacco than in tobacco smokers. At present, there is no direct evidence that marijuana smoking induces lung cancer that is comparable to the well-documented association between tobacco smoking and lung cancer, although it should be emphasized that heavy marijuana use among Americans may be of too brief duration for detection of this problem.
Although marijuana has also been associated with adverse effects on a number of other systems, many of these studies await replication and confirmation. For example, the reported correlation between marijuana use and decreased testosterone levels in males has not been confirmed. Decreased sperm count and motility and abnormalities of morphology of spermatozoa following marijuana use have also been reported. Administration of high doses of marijuana to female rhesus monkeys has revealed significant marijuana-induced suppression of pituitary gonadotrophins and gonadal steroids. Carefully conducted prospective studies demonstrated a significant correlation between impaired fetal growth and development and heavy marijuana use during pregnancy. Marijuana also has been implicated in derangements of the immune response system, in chromosomal abnormalities, and in inhibition of DNA, RNA, and protein synthesis, but these findings have not been confirmed or related to any specific physiologic effect of marijuana in humans. One report of cannabis-induced brain atrophy in young adults has not been confirmed in studies of computerized tomography with young men who had documented histories of heavy marijuana smoking.
Tolerance and physical dependence Habitual marijuana users rapidly develop tolerance to the psychoactive effects of marijuana, often smoking more frequently and trying to secure more potent cannabis compounds. Tolerance for physiologic effects of marijuana develops at different rates; e.g. tolerance for marijuana-induced tachycardia develops rapidly, but tolerance for marijuana-induced conjunctival injection develops more slowly. Tolerance to both behavioral and physiologic effects of marijuana decreases rapidly upon cessation of marijuana use.
Mild to moderate withdrawal signs and symptoms have been reported in chronic cannabis users, with severity of symptoms related to dosage and duration of use. These include tremor, sweating, nausea, vomiting, diarrhea, irritability, anorexia, and sleep disturbances. Withdrawal signs and symptoms observed in chronic marijuana users are usually relatively mild in comparision to those observed with heavy opiate or alcohol users and rarely require medical or pharmacologic intervention. Somewhat more severe and protracted abstinence syndromes may occur after sustained use of high potency cannabis compounds for long periods.