Marijuana Myths and Facts.


This collection of myths and facts is based on the book
Marijuana Myths, Marijuana Facts: A Review of the Scientific Evidence . A decade after the book was published, the latest scientific evidence continues to support the original findings.

Marijuana Myths, Marijuana Facts is a book by Lynn Zimmer PHD. and John P. Morgan MD.

Myth: Marijuana Can Cause Permanent Mental Illness
. Among adolescents, even occasional marijuana use may cause psychological damage. During intoxication, marijuana users become irrational and often behave erratically.

Fact: There is no convincing scientific evidence that marijuana causes psychological damage or mental illness in either teenagers or adults. Some marijuana users experience psychological distress following marijuana ingestion, which may include feelings of panic, anxiety, and paranoia. Such experiences can be frightening, but the effects are temporary. With very large doses, marijuana can cause temporary toxic psychosis. This occurs rarely, and almost always when marijuana is eaten rather than smoked. Marijuana does not cause profound changes in people's behavior.

Iverson, Leslie. “Long-term effects of exposure to cannabis.” Current Opinion in Pharmacology5(2005): 69-72.
Weiser and Noy. “Interpreting the association between cannabis use and increased risk of schizophrenia.” Dialogues in Clincal Neuroscience1(2005): 81-85.

"Cannabis use will impair but not damage mental health." London Telegraph. 23 January 2006.
Andreasson, S. et al. “Cannabis and Schizophrenia: A Longitudinal study of Swedish Conscripts,” The Lancet  2 (1987): 1483-86.
Degenhardt, Louisa, Wayne Hall and Michael Lynskey.  “Testing hypotheses about the relationship between cannabis use and psychosis,” Drug and Alcohol Dependence 71 (2003): 42-4.
Weil, A. “Adverse Reactions to Marijuana: Classification and Suggested Treatment.” New England Journal of Medicine 282 (1970): 997-1000.

Myth: Marijuana Causes Crime. Marijuana users commit more property offenses than nonusers. Under the influence of marijuana, people become irrational, aggressive, and violent.

Fact: Every serious scholar and government commission examining the relationship between marijuana use and crime has reached the same conclusion: marijuana does not cause crime. The vast majority of marijuana users do not commit crimes other than the crime of possessing marijuana. Among marijuana users who do commit crimes, marijuana plays no causal role. Almost all human and animal studies show that marijuana decreases rather than increases aggression.

Fagan, J., et al. “Delinquency and Substance Use Among Inner-City Students.” Journal of Drug Issues20 (1990): 351-402.
Johnson, L.D., et al. “Drugs and Delinquency: A Search for Causal Connections.”  Ed. D.B. Kandel.Longitudinal Research on Drug Use: Empirical Findings and Methodological Issues. New York: John Wiley & Sons, 1978. 137-156.
Goode, E. “Marijuana and Crime.” Marihuana: A Signal of Misunderstanding, Appendix I. National Commission on Marihuana and Drug Abuse Washington, DC: U.S. Government Printing Office, 1972. 447-453.
Abram, K.M. and L.A. Teplin. “Drug Disorder, Mental Illness, and Violence.” Drugs and Violence: Causes, Correlates, and Consequences. Rockville: National Institute on Drug Abuse, 1990. 222-238.
Cherek, D.R., et al. “Acute Effects of Marijuana Smoking on Aggressive, Escape and Point-Maintained Responding of Male Drug Users.”Psychopharmacology 111 (1993): 163-168.
Tinklenberg, J.R., et al. “Drugs and criminal assaults by adolescents: A Replication Study.” Journal of Psychoactive Drugs 13 (1981): 277-287.
Myth: Marijuana Interferes With Male and Female Sex Hormones. In both men and women, marijuana can cause infertility. Marijuana retards sexual development in adolescents. It produces feminine characteristics in males and masculine characteristics in females.

Fact: There is no evidence that marijuana causes infertility in men or women. In animal studies, high doses of THC diminish the production of some sex hormones and can impair reproduction. However, most studies of humans have found that marijuana has no impact of sex hormones. In those studies showing an impact, it is modest, temporary, and of no apparent consequence for reproduction. There is no scientific evidence that marijuana delays adolescent sexual development, has feminizing effect on males, or a masculinizing effect on females.

Parents Resource Institute for Drug Education.Marijuana and Cocaine. Atlanta, GA: PRIDE, 1990.
Center for Substance Abuse Prevention. Female Adolescents and Marijuana Use; Fact Sheet for Adults. Rockville: U.S. Department of Health and Human Services, 1995.
Center for Substance Abuse Prevention. Marijuana: Tips for Teens. Rockville: U.S. Department of Health and Human Services, 1995.
Swan, Neil. “A Look at Marijuana’s Harmful Effects.”NIDA Notes. 9:2 (1994): 16.
Clinton, President Bill. Speech at Framingham High School. Framingham, Massachusetts. 20 Oct. 1994.
Myth: Marijuana Use During Pregnancy Damages the Fetus. Prenatal marijuana exposure causes birth defects in babies, and, as they grow older, developmental problems. The health and well being of the next generation is threatened by marijuana use by pregnant women.

Fact: Studies of newborns, infants, and children show no consistent physical, developmental, or cognitive deficits related to prenatal marijuana exposure. Marijuana had no reliable impact on birth size, length of gestation, neurological development, or the occurrence of physical abnormalities. The administration of hundreds of tests to older children has revealed only minor differences between offspring of marijuana users and nonusers, and some are positive rather than negative. Two unconfirmed case-control studies identified prenatal marijuana exposure as one of many factors statistically associated with childhood cancer. Given other available evidence, it is highly unlikely that marijuana causes cancer in children.

Mann, Peggy. The Sad Story of Mary Wanna. NY: Woodmere Press, 1988. 30.
Fried, Peter. Quoted in “Marijuana: Its Use and Effects.” Prevention Pipeline. 8:5 (1995): 4.
American Council for Drug Education. Drugs and Pregnancy. Rockville: Phoenix House, 1994.
Swan, Neil. “A Look at Marijuana’s Harmful Effects.”NIDA Notes. 9. 2 (1994): 16.
Parents Resource Institute for Drug Education.Marijuana – Effects on the Female. Atlanta, GA: PRIDE, 1996.

Myth: Marijuana Use Impairs the Immune System. Marijuana users are at increased risk of infection, including HIV. AIDS patients are particularly vulnerable to marijuana's immunopathic effects because their immune systems are already suppressed.

Fact: There is no evidence that marijuana users are more susceptible to infections than nonusers. Nor is there evidence that marijuana lowers users' resistance to sexually transmitted diseases. Early studies which showed decreased immune function in cells taken from marijuana users have since been disproved. Animals given extremely large doses of THC and exposed to a virus have higher rates of infection. Such studies have little relevance to humans. Even among people with existing immune disorders, such as AIDS, marijuana use appears to be relatively safe. However, the recent finding of an association between tobacco smoking and lung infection in AIDS patients warrants further research into possible harm from marijuana smoking in immune suppressed persons.

Parents Resource Institute for Drug Education.Marijuana and Cocaine. Atlanta: PRIDE, 1990.
Preate, Ernest D. Blowing Away the Marijuana Smokescreen. Scranton: Pennsylvania Office of Attorney General, [no date]: 2.
Spence, W.R. Marijuana: Its Effects and Hazards. Waco: Health Edco, [no date].
Voth, Eric A. The International Drug Strategy Institute Position Paper on the Medical Applications of Marijuana. Omaha: Drug Watch International, [no date].
Drug Watch International. By Any Modern Medical Standard, Marijuana is No Medicine. Omaha: Drug Watch International, [no date].
Myth: Marijuana's Active Ingredient, THC, Gets Trapped in Body Fat. Because THC is released from fat cells slowly, psychoactive effects may last for days or weeks following use. THC's long persistence in the body damages organs that are high in fat content, the brain in particular.

Fact: Many active drugs enter the body's fat cells. What is different (but not unique) about THC is that it exits fat cells slowly. As a result, traces of marijuana can be found in the body for days or weeks following ingestion. However, within a few hours of smoking marijuana, the amount of THC in the brain falls below the concentration required for detectable psychoactivity. The fat cells in which THC lingers are not harmed by the drug's presence, nor is the brain or other organs. The most important consequence of marijuana's slow excretion is that it can be detected in blood, urine, and tissue long after it is used, and long after its psychoactivity has ended.

Committees of Correspondence. Drug Abuse Newsletter 16 (March 1984).
Mann, Peggy. Marijuana Alert. New York: McGraw-Hill Book Company. 1985. 184.
Nahas, Gabriel. "When Friends of Patients Ask About Marihuana." Journal of the American Medical Association 233 (1979): 79.
DuPont, Robert. Getting Tough on Gateway Drugs. Washington, DC: American Psychiatric Press, 1984. 68.
Myth: Marijuana Use is a Major Cause Of Highway Accidents. Like alcohol, marijuana impairs psychomotor function and decreases driving ability. If marijuana use increases, an increase in of traffic fatalities is inevitable.

Fact: There is no compelling evidence that marijuana contributes substantially to traffic accidents and fatalities. At some doses, marijuana affects perception and psychomotor performances- changes which could impair driving ability. However, in driving studies, marijuana produces little or no car-handling impairment- consistently less than produced by low moderate doses of alcohol and many legal medications. In contrast to alcohol, which tends to increase risky driving practices, marijuana tends to make subjects more cautious. Surveys of fatally injured drivers show that when THC is detected in the blood, alcohol is almost always detected as well. For some individuals, marijuana may play a role in bad driving. The overall rate of highway accidents appears not to be significantly affected by marijuana's widespread use in society.

Center on Addiction and Substance Abuse. “Legalization: Panacea or Pandora’s Box”. New York. (1995):36.
Swan, Neil. “A Look at Marijuana’s Harmful Effects.”NIDA Notes. 9.2 (1994): 14. 
Moskowitz, Herbert and Robert Petersen. Marijuana and Driving: A Review. Rockville: American Council for Drug Education, 1982. 7.
Mann, Peggy. Marijuana Alert. New York: McGraw-Hill, 1985. 265.
Myth: Marijuana Related Hospital Emergencies Are Increasing, Particularly Among Youth. This is evidence that marijuana is much more harmful than most people previously believed.

Fact: Marijuana does not cause overdose deaths. The number of people in hospital emergency rooms who say they have used marijuana has increased. On this basis, the visit may be recorded as marijuana-related even if marijuana had nothing to do with the medical condition preceding the hospital visit. Many more teenagers use marijuana than use drugs such as heroin and cocaine. As a result, when teenagers visit hospital emergency rooms, they report marijuana much more frequently than they report heroin and cocaine. In the large majority of cases when marijuana is mentioned, other drugs are mentioned as well. In 1994, fewer than 2% of drug related emergency room visits involved the use of marijuana.

Brown, Lee. Quoted in U.S. Department of Health and Human Services Press Release, National Drug Survey Results Released with New Youth Public Education Materials. Rockville: 12 September 1995.
Shalala, Donna. "Say ‘No’ to Legalization of Marijuana." Wall Street Journal 18 August 1995: A10.
Shuster, Charles. Quoted in Drug Enforcement Administration. Drug Legalization: Myths and Misconceptions. Washington, DC: U.S. Department of Justice, 1994. 5.
Myth: Marijuana Use Can Be Prevented. Drug education and prevention programs reduced marijuana use during the 1980s. Since then, our commitment has slackened, and marijuana use has been rising. By expanding and intensifying current anti-marijuana messages, we can stop youthful experimentation.

Fact: There is no evidence that anti-drug messages diminish young people's interest in drugs. Anti-drug campaigns in the schools and the media may even make drugs more attractive. Marijuana use among youth declined throughout the 1980s, and began increasing in the 1990s. This increase occurred despite young people's exposure to the most massive anti-marijuana campaign in American history. In a number of other countries, drug education programs are based on a "harm reduction" model, which seeks to reduce the drug-related harm among those young people who do experiment with drugs.

Center on Addiction and Substance Abuse. "National Survey of American Attitudes on Substance Abuse." New York (1995):28.
Brown, Lee. Director of National Drug Control Policy, remarks at National Conference on Marijuana Use: Prevention, Treatment, and Research. Sponsored by the National Institute on Drug Abuse, Arlington, VA (July 1995).
Califano, Joseph A. "Don’t Stop This War."Washington Post 26 May 1996: C7.
Shalala, Donna. "Marijuana: A Recurring Problem."Prevention Pipeline 8.5 (1995): 2.
Burke, James. [Partnership for a Drug-Free America]. Interview. MS-NBC with Tom Brokaw. MS-NBC, 3 September 1996.
Falco, Mathea. The Making of a Drug-Free America: Programs That Work. New York: Times Books, 1992. 202.

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