Marijuana: Just the facts please

Eddy Elmer and Rosie Hayter,
University of Toronto Student Health Outreach Program

University of Toronto Health Service: ShopTalk, April 1998

Marijuana is the most widely used illegal drug in the United States (U.S. Department of Health and Human Services 1991), and for several years now there have been calls to legalise its use. However, health officials continue to warn of the dangers posed by even occasional marijuana use.

Marijuana (also popularly referred to as pot, weed, grass, or dope) is a derivative of the dried leaves, stems, and flowering tops of the hemp (or Cannabis sativa) plant. This plant is often harvested for use in the manufacture of rope, paper, fabric, and other commercial products.

The active ingredient in marijuana is tetrahydrocannabinol (THC). In ordinary marijuana, the concentration of THC is about 3%. Higher concentrations are found in marijuana derivatives. For instance, the resin on the leaves of the maturing female hemp plant are often dried and used to produce hashish and hash oil, with THC concentrations of 3.6% and 16% respectively. Sinsmella, another strong variant, is made from the plant's buds and flowering tops, and has an average of 7.5% THC (U.S. Department of Health and Human Services 1995).

Marijuana can be eaten or used in beverages such as tea, but is usually smoked (as a cigarette, or "joint") because the large surface of the lungs is able to absorb it more efficiently than the gastrointestinal system, thus allowing THC to reach the brain more quickly. Some people prefer an even faster induction, thus smoking marijuana through pipes, including large water pipes called bongs.

THC passes rapidly from the bloodstream to the brain and fatty tissues. Once in the brain, it appears to congregate in the hippocampus (implicated in learning and memory), the cerebral cortex (involved in complex thought processes and perception), and the cerebellar cortex (involved in motor coordination) (e.g. Devane et al. 1988).

Marijuana affects everyone differently. A given user's reaction depends on the following: type of marijuana ingested; the user's expectations of its effects; the environment in which the drug is administered; method of induction; concurrent use with other psychoactive substances; present medical conditions, and previous use of the drug.

Thus, given the variability of individual reactions, one long-term user may experience few adverse effects while another may experience many. In fact, another one-time user might experience some of the same deleterious effects that a long-time user might experience.

Those taking marijuana often speak of feeling stimulated after ingestion. Others report experiencing hallucinations or becoming bizarrely fascinated/entertained by normal sights, sounds, smells, or events. Some people report feeling more "relaxed," whereas others report feeling nothing at all.

Many people display outward signs of a "high," including appearing dizzy, maintaining an unsteady gait, acting silly for no apparent reason, developing very red, bloodshot eyes, and appearing to have difficulty remembering very recent events (e.g. Heishman et al. 1997).

Many people experience a feeling of time lag. Some even become incredibly thirsty or hungry. Heart palpitations may occur. Some users (especially those taking stronger concentrations) may experience sudden anxiety or panic attacks, or even psychotic symptoms requiring emergency treatment (e.g. Thomas 1996). Paranoid thoughts are not uncommon.

The immediate effects of marijuana, whether or not the user is aware of them, normally reside within 2 to 3 hours. As the effects subside, sleepiness may occur.

However, unlike alcohol and other substances of which the body disposes fairly quickly, THC can remain in the body for days, or even weeks, and still produce the sensations and reactions of a "high"—often in the absence of any overt signs of marijuana use.

These more immediate effects aside, marijuana can also lead to more serious (and irreversible) problems.

First, since any amount of marijuana adversely affects timing, co-ordination, judgment (e.g. judgment of road distances), and reasoning, driving or operating heavy machinery while under the influence of marijuana can pose severe dangers.

With respect to longer-term health dangers, the jury is still out. But the mere possibility that using marijuana, especially in larger quantities or for extended periods, might cause longer-lasting or permanent organic damage should be sufficient reason to be very cautious.

Regular marijuana use has been linked to cognitive deficits (e.g. Block and Ghoneim 1993) and increased immune system susceptibility to infectious disease, cancer, and AIDS (e.g. Baldwin et al. 1997).

It has also been linked to reproductive system abnormalities (e.g. Wenger et al. 1992), including infertility (e.g. Mueller et al. 1990). Use during pregnancy has been linked to newborn tremors, startles, sleep problems, and reduced visual attention to the environment (e.g., Dahl et al. 1995; Fried and Makin 1987).

It should be noted that marijuana can become addicting (e.g. Fonseca et al. 1997), and though a less frequent user may not put him/herself in as much danger of developing the more serious or longer-term problems noted above, addiction will increase the likelihood that marijuana will be used with increasing frequency, which could, ultimately, cause grave health concerns.


REFERENCES


Baldwin GC, Tashkin DP, Buckley DM, Park AN, Dubinett SM, Roth MD. Marijuana and cocaine impair alveolar macrophage function and cytokine production. Am J Respir Crit Care Med 156:1606-1613, 1997.

Block RI, Ghoneim MM. Effects of chronic marijuana use on human cognition. Psychopharmacology 110:219-228, 1993.

Dahl RE, Scher MS, Williamson DE, Robles N, Day N. A longitudinal study of prenatal marijuana use: Effects on sleep and arousal at age 3 years. Archives of Pediatric and Adolescent Medicine 149:145-150, 1995.

Devane WA, Hanus L, Breuer A, Pertwee RG, Stevenson LA, Griffin G, Gibsdon D, Mandelbaum A, Etinger A, Mechoulam R. Isolation and structure of a brain constituent that binds the cannabinoid receptor. Science 258:1946-1949, 1992.

Fonseca FR, Rocio M, Carrera A, Navarro M, Koob GF, Weiss F. Activation of corticotropin-releasing factor in the limbic system during cannabinoid withdrawal. Science 276:2050-2054, 1997.

Fried PA, Makin JE. Neonatal behavioral correlates of prenatal exposure to marijuana, cigarettes, and alcohol in a low risk population. Neurobehavioral Toxicology and Teratology 9:1-7, 1987.

Heishman SJ, Arasteh K, Stitzer ML. Comparative effects of alcohol and marijuana on mood, memory, and performance. Pharamcol Biochem Behav 58: 93-101, 1997.

Mueller BA, Daling JR, Weiss NS, Moore DE. Recreational drug use and the risk of primary infertility. Epidemiology 1:195-200, 1990.

Thomas, H. A community survey of adverse effects of cannabis use. Drug Alcohol Depend 42:201-207, 1996.

U.S. Department of Health and Human Services. Drug abuse and drug abuse research: The third triennial report to Congress. Rockville, MD, National Institute on Drug Abuse, 1991.

U.S. Department of Health and Human Services. Marijuana facts parents need to know. Rockville, MD, National Institute on Drug Abuse, 1995.

Wenger T, Croix D, Tramu G, Leonardelli J. Marijuana and reproduction: Effects on puberty and gestation in female rats. Ann Endocrinol 53:37-43, 1992.