Effects of Marijuana


Marijuana is the most widely used illicit drug in the country. Some 4.3 percent of Americans have been dependent on marijuana, as defined in the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision (DSM-IV-TR; American Psychiatric Association, 2000), at some time in their lives. Marijuana produces dependence less readily than most other illicit drugs, but nonetheless is addictive. Some 9 percent of those who try marijuana develop dependence compared to, for example, 15 percent of people who try cocaine and 24 percent of those who try heroin. However, because so many people use marijuana, cannabis dependence is twice as prevalent as dependence on any other illicit psychoactive substance (Anthony and Helzer, 1991; Anthony, Warner, and Kessler, 1994).

After declining steadily through 1990, statistics have shown the number of workers’ compensation-related claims with drug use have increased precipitously. “Employed drug abusers cost their employers about twice as much in medical and workers’ compensation claims as their drug-free coworkers,” according to the National Institute on Drug Abuse.

Marijuana exhibits negative effects on school performance, known health risks for young people, has driving hazards associated with it and possesses potential harm to pregnant women and others who become regular users, altogether presenting a convincing argument against its use

Marijuana and hashish come from the hemp plant, cannabis sativa, which grows throughout most of the tropical and temperate zones of the world. Marijuana is typically sold in the form of cut, dried leaves, stems and flowers of this plant. It is generally smoked like a cigarette or cigar, or in pipes. In loosely rolled cigarettes it is called a joint. Such joints are often laced with a number of adulterants such as PCP, thus altering and increasing the effects of toxicity. Sometimes it’s eaten.

Cannabis is a generic name for a variety of preparations derived from the plant Cannabis sativa. A sticky resin which covers the flowering tops and upper leaves, most abundantly in the female plant, contains more than 60 cannabinoids substances. Laboratory research on animals and humans has demonstrated that the primary psychoactive constituent in cannabis is the cannabinoids, delta-9-tetrahydrocannabinol or THC.

Hashish or hash consists of dried cannabis resin and compressed flowers. The concentration of THC in hashish generally ranges from 2-8 per cent, although it can be as high as 10-20 per cent. Hash oil is a highly potent and viscous substance obtained by extracting THC from hashish (or marijuana) with an organic solvent, concentrating the filtered extract, and in some cases subjecting it to further purification.

Testing Techniques
The initial screening cutoff level is 50-ng/ml as this test looks not only at THC but also several similar metabolites. The GC/MS cutoff level is 15-ng/ml and is specific for THC. The elimination half-life of marijuana ranges from 14-38 hours. At the initial cutoff of 50-ng/ml, the daily user will remain positive from 7 to 30 days after cessation. At the confirmation level of 15- ng/ml, the frequent user will be positive for perhaps as long as 15 weeks. Marijuana metabolites’ storage and slow release from lipid tissues is the reason for this long detection period.

The Effects
The major active ingredient in marijuana and hashish is tetrahydrocannabinol (THC). The exact nature of its action is not entirely understood, although it is believed to change to a psychoactive compound in the liver. The higher the THC content the stronger the effects. The average potency of marijuana in this country has increased since the 1970s.

The effect is usually accompanied by a state of altered perception, particularly of distance and time. The euphoric feeling usually peaks within ten to thirty minutes of smoking marijuana, but residual effects may persist much longer. Marijuana and hashish can impair balance, coordination, speech and thinking. Even small amounts of marijuana have been found to adversely affect driving performance.

Marijuana Implicated in Auto Accidents
Available marijuana, whether for “medical” purposes or recreational purposes, will add to the drug’s growing contribution to traffic accidents. An April 2000 review of two National Highway Traffic Safety Administration studies found that alcohol remains the predominant drug in fatal crashes, but marijuana is the drug next most frequently found in drivers involved in crashes. Both alcohol and marijuana are often found together in drivers involved in motor vehicle crashes. A National Household Survey of Drug Abuse found that more than one fourth of the 166 million drivers age sixteen and older occasionally drive under the influence of alcohol, marijuana, or both.

Acute Psychological and Health Effects
The major reason for the widespread recreational use of cannabis is that it produces a “high”, an altered state of consciousness which is characterized by mild euphoria, relaxation, and perceptual alterations, including time distortion and the intensification of ordinary sensory experiences, such as eating, watching films, and listening to music.

The inhalation of marijuana smoke, or the ingestion of THC, has a number of bodily effects. Among these the most dependable is an increase in heart rate of 20-50 per cent over baseline, which occurs within a few minutes to a quarter of an hour, and lasts for up to three hours. Changes in blood pressure also occur, which depend upon posture: blood pressure is increased while the person is sitting, and decreases while standing.

Psychomotor Effects and Driving
The major potential health risk from the acute use of cannabis arises from its effects on psychomotor performance. Intoxication produces dose-related impairments in a wide range of cognitive and behavioral functions that are involved in skilled performances like driving automobile or operating machinery. The negative effects of cannabis on the performance of psychomotor tasks are almost always related to dose. The effects are generally larger, more consistent and of increased persistence in difficult tasks which involve sustained attention. The acute effects of doses of cannabis are subjectively equivalent to or higher than usual recreational doses on driving performance in laboratory simulators to those of alcohol.

Cognitive Effects
There is reasonable clinical and experimental evidence, the long-term use of cannabis may produce more subtle cognitive impairment in the higher cognitive functions of memory, attention and organization and integration of complex information. These impairments may affect everyday functioning, particularly in those with marginal educational aptitude, and among adults in occupations that require high levels of cognitive capacity. The evidence suggests that the longer the period that cannabis has been used, the more pronounced is the cognitive impairment. It remains to be seen whether the impairment can be reversed by abstinence from cannabis.

References are available upon request.