Cannabis is a leafy plant which grows wild in many of the tropic and temperate areas of the world. It is cultivated both indoors and out for the production of its flowering tops. The most commonly used form of cannabis are the leaves and flowering tops (buds) which may be either smoked or eaten; It also comes in a more concentrated resinous form called hashish, and as a sticky black liquid called hash oil. There are three distinct genera of cannabis: Cannabis sativa, Cannabis indica, and Cannabis ruderalis. Most recreationally used cannabis is the result of interbreeding between these three types. The term 'hemp' is generally used to describe low-thc varieties of cannabis which are grown for industrial uses.
Health and safetyEdit
Effects on the BrainEdit
Scientists have learned a great deal about how THC acts in the brain to produce its many effects. When someone smokes marijuana, THC rapidly passes from the lungs into the bloodstream, which carries the chemical to the brain and other organs throughout the body.
THC acts upon specific sites in the brain, called cannabinoid receptors, kicking off a series of cellular reactions that ultimately lead to the “high” that users experience when they smoke marijuana. Some brain areas have many cannabinoid receptors; others have few or none. The highest density of cannabinoid receptors are found in parts of the brain that influence pleasure, memory, thoughts, concentration, sensory and time perception, and coordinated movement.
Not surprisingly, marijuana intoxication can cause distorted perceptions, impaired coordination, difficulty in thinking and problem solving, and problems with learning and memory. Research has shown that marijuana’s adverse impact on learning and memory can last for days or weeks after the acute effects of the drug wear off. As a result, someone who smokes marijuana every day may be functioning at a suboptimal intellectual level all of the time.
Research on the long-term effects of marijuana abuse indicates some changes in the brain similar to those seen after long-term abuse of other major drugs. For example, cannabinoid withdrawal in chronically exposed animals leads to an increase in the activation of the stress-response system and changes in the activity of nerve cells containing dopamine. Dopamine neurons are involved in the regulation of motivation and reward, and are directly or indirectly affected by all drugs of abuse.
Effects on the LungsEdit
Numerous studies have shown marijuana smoke to contain carcinogens and to be an irritant to the lungs. In fact, marijuana smoke contains 50–70 percent more carcinogenic hydrocarbons than does tobacco smoke. Marijuana users usually inhale more deeply and hold their breath longer than tobacco smokers do, which further increase the lungs’ exposure to carcinogenic smoke. Marijuana smokers show dysregulated growth of epithelial cells in their lung tissue, which could lead to cancer; however, a recent case-controlled study found no positive associations between marijuana use and lung, upper respiratory, or upper digestive tract cancers. Thus, the link between marijuana smoking and these cancers remains unsubstantiated at this time.
Nonetheless, marijuana smokers can have many of the same respiratory problems as tobacco smokers, such as daily cough and phlegm production, more frequent acute chest illness, and a heightened risk of lung infections. A study of 450 individuals found that people who smoke marijuana frequently but do not smoke tobacco have more health problems and miss more days of work than nonsmokers. Many of the extra sick days among the marijuana smokers in the study were for respiratory illnesses.
Effects on the HeartEdit
Marijuana increases heart rate by 20–100 percent shortly after smoking; this effect can last up to 3 hours. In one study, it was estimated that marijuana users have a 4.8-fold increase in the risk of heart attack in the first hour after smoking the drug. This may be due to the increased heart rate as well as effects of marijuana on heart rhythms, causing palpitations and arrhythmias. This risk may be greater in aging populations or those with cardiac vulnerabilities.
Effects on Mental HealthEdit
A number of studies have shown an association between chronic marijuana use and increased rates of anxiety, depression, suicidal ideation, and schizophrenia. Some of these studies have shown age at first use to be a factor, where early use is a marker of vulnerability to later problems. However, at this time, it is not clear whether marijuana use causes mental problems, exacerbates them, or is used in attempt to self-medicate symptoms already in existence. Chronic marijuana use, especially in a very young person, may also be a marker of risk for mental illnesses, including addiction, stemming from genetic or environmental vulnerabilities, such as early exposure to stress or violence. At the present time, the strongest evidence links marijuana use and schizophrenia and/or related disorders. High doses of marijuana can produce an acute psychotic reaction; in addition, use of the drug may trigger the onset or relapse of schizophrenia in vulnerable individuals.
Other effects include dry mouth ("pasties" or "cotton mouth"), increased appetite ("munchies"), and "red-eye". The first is a common effect from smoking anything. THC activates parts of the brain (Cannabinoid receptors) which are linked to appetite. (It is believed that cannabinoid receptors are activated after birth to make an infant hungry until they can learn the daily routine of eating). THC also causes dilation of blood vessels which can lead to the "red-eye". THC can also lower intra-ocular (eye) pressure making it useful as a treatment for glaucoma.
Cannabis has an anti-nauseante property. However, like most antiemetics, this effect is seemingly reversed with higher doses.
Long-term marijuana abuse can lead to addiction; that is, compulsive drug seeking and abuse despite its known harmful effects upon social functioning in the context of family, school, work, and recreational activities. Long-term marijuana abusers trying to quit report irritability, sleeplessness, decreased appetite, anxiety, and drug craving, all of which make it difficult to quit. These withdrawal symptoms begin within about 1 day following abstinence, peak at 2–3 days, and subside within 1 or 2 weeks following drug cessation.
Use and AppealEdit
Cannabis is one of the most commonly abused drugs. Effects include relaxation, fatigue, increased emotional reaction (e.g., laughter), and muscle relaxation.
The effects typically subside between 1 and 4 hours after smoking, depending on the users body build.
Effects on Daily LifeEdit
Research clearly demonstrates that marijuana has the potential to cause problems in daily life or make a person’s existing problems worse. In one study, heavy marijuana abusers reported that the drug impaired several important measures of life achievement including physical and mental health, cognitive abilities, social life, and career status. Several studies associate workers’ marijuana smoking with increased absences, tardiness, accidents, workers’ compensation claims, and job turnover.
Hemp can be used to make paper, textiles (clothing, furniture upholstery, sails, etc.), fuel, and food. It can be grown rather easily and harvested several times annually.
- Herkenham M, Lynn A, Little MD, et al. Cannabinoid receptor localization in the brain. Proc Natl Acad Sci, USA 87(5):1932–1936, 1990.
- Pope HG, Gruber AJ, Hudson JI, Huestis MA, Yurgelun-Todd D. Neuropsychological performance in long-term cannabis users. Arch Gen Psychiatry 58(10):909–915, 2001.
- Rodríguez de Fonseca F, Carrera MRA, Navarro M, Koob GF, Weiss F. Activation of corticotropin-releasing factor in the limbic system during cannabinoid withdrawal. Science 276(5321):2050–2054, 1997.
- Diana M, Melis M, Muntoni AL, Gessa GL. Mesolimbic dopaminergic decline after cannabinoid withdrawal. Proc Natl Acad Sci, USA 95(17):10269–10273, 1998.
- Tashkin DP. Smoked marijuana as a cause of lung injury. Monaldi Arch Chest Dis 63(2):92–100, 2005.
- Hashibe M, Morgenstern H, Cui Y, et al. Marijuana use and the risk of lung and upper aerodigestive tract cancers: Results of a population-based case-control study. Cancer Epidemiol Biomarkers Prev 15(10):1829–1834, 2006
- Polen MR, Sidney S, Tekawa IS, Sadler M, Friedman GD. Health care use by frequent marijuana smokers who do not smoke tobacco. West J Med 158(6):596–601, 1993.
- Mittleman MA, Lewis RA, Maclure M, Sherwood JB, Muller JE. Triggering myocardial infarction by marijuana. Circulation 103(23):2805–2809, 2001.
- Moore TH, Zammit S, Lingford-Hughes A, et al. Cannabis use and risk of psychotic or affective mental health outcomes: A systematic review. Lancet 370 (9584):319–328, 2007.
- Budney AJ, Vandrey RG, Hughes JR, Thostenson JD, Bursac Z. Comparison of cannabis and tobacco withdrawal: Severity and contribution to relapse. J Subst Abuse Treat, e-publication ahead of print, March 12, 2008.
- Gruber AJ, Pope HG, Hudson JI, Yurgelun-Todd D. Attributes of long-term heavy cannabis users: A case control study. Psychological Med 33(8):1415–1422, 2003.