Fiction: Marijuana Is Harmless

Fact: Marijuana is harmful.

The Brain

  • Smoking marijuana leads to some changes in the brain similar to those caused by cocaine, heroin and alcohol.
  • According to Dr. Marvin Seppala, the Chief Medical Officer at the Hazelden Foundation, a prominent drug recovery center in Minnesota, "The younger people begin using marijuana, especially before the age of 21, the likelier they are to become addicted to an addictive substance. Their addiction is both physiological and psychological. Studies on the brain have shown that pot use alters the hippocampus and affects short-term memory. As an adolescent, there are remarkable experiences that contribute to growth. These need to be set down into memory—and pot use stops this."

Lung Damage

  • Regular marijuana users often develop breathing problems including chronic coughing and wheezing. Marijuana contains the same cancer-causing chemicals as tobacco. The amount of tar inhaled by marijuana smokers and the level of carbon monoxide absorbed by those who smoke marijuana, regardless of THC content, are three to five times greater than among tobacco smokers. Smoking five marijuana cigarettes is equal to smoking a full pack of tobacco cigarettes. According to the American Lung Association, there is 50-70% more cancer causing material in marijuana smoke than in cigarette smoke. In fact, marijuana smoke contains more than 400 chemicals.
  • In an article in the Journal of General Internal Medicine respected scientists at Yale University concluded that smoking marijuana is associated with an increased risk of many of the same respiratory problems that afflict cigarette smokers including shortness of breath, wheezing, chronic bronchitis, coughing and phlegm.2 Researchers also found that marijuana smoking may also expose a user's respiratory system to infectious organisms such as molds and fungi. That's because many marijuana plants are already contaminated with different kinds of fungal spores.
  • Marijuana proponents will tell you that bong water pipes will filter out these toxins. In fact, marijuana's primary cancer-causing tar, benzopyrene, does not dissolve in water. That means a bong cannot protect your lungs from this danger.

Mental Health

  • For young users, marijuana can lead to increased anxiety, panic attacks, depression and other mental health problems. For those already prone to depression or anxiety attacks, marijuana use may accelerate or exacerbate problems.
  • The United Kingdom Department of Health acknowledged in January, 2004 that cannabis is an “important causal factor” in mental illness. A spokesman for the Department said that “There is medical clinical evidence now that there is an important causal factor between cannabis use and schizophrenia—not the only factor, but an important causal factor. That is the common consensus among the medical fraternity.”3
  • A British mental health organization, Rethink, reported that “there had been a 60% increase in people who had smoked (cannabis) and had mental problems in the last five years.4
  • A study conducted by Maastricht University (Netherlands) and published in the British Medical Journal reported that frequent cannabis use during adolescence and young adulthood raises the risk of psychotic symptoms later in life.5

Fact: Marijuana interferes with driving abilities.

  • Marijuana affects alertness, concentration, perception, coordination and reaction time, many of the skills required for safe driving and other tasks. These effects can last several hours after smoking marijuana. Marijuana use can also make it difficult to judge distances and react to signals and sounds on the road.
  • Research has provided more evidence of the prevalence of drugged driving and the resulting consequences. A roadside study of reckless drivers who were not impaired by alcohol showed that 45% tested positive for marijuana.6
  • Research conducted by the University of Auckland, New Zealand, proves the link between marijuana use and car accidents. The research found that habitual cannabis users were 9.5 times more likely to be involved in crashes, with 5.6% of people who had crashed having taken the drug, compared to 0.5% of the control group.7

Fact: Marijuana is linked to risky behaviors.

  • Research shows that kids who use marijuana in early adolescence are more likely to engage in risky behaviors that may put their futures in jeopardy, such delinquency; having multiple sexual partners; perceiving drugs as not harmful; and having more friends who exhibit deviant behavior.8
  • Despite popular notions, research has shown a link between frequent marijuana use and increased violent behavior. Research found that among youth, the incidence of physically attacking people, destroying property and stealing increased in proportion to the number of days marijuana was smoked in the past year.
  • In 2002, approximately 21 percent of youths (5 million) engaged in serious fighting at school or work, almost 16 percent (4 million) took part in a group-against-group fight, and almost 8 percent (2 million) attacked someone with the intent to seriously hurt them during the past year. Nearly 5 percent of youths (1.2 million) stole or tried to steal something worth more than $50, more than 4 percent (1.1 million) sold illegal drugs, and more than 3 percent (800,000) carried a handgun during the past year. The percentages of youths engaging in delinquent behaviors in the past year rose with increasing frequency of marijuana use.8
  • According to the National Household Survey on Drug Abuse (now the National Survey on Health) adolescents 12-17 who use marijuana weekly are nine times more likely than non-users to experiment with other illegal drugs or alcohol, five times more likely to steal and nearly four times more likely to engage in violence.9

Fact: Marijuana affects learning and academic achievement.

  • Researchers have found that heavy marijuana use impairs the ability of young people to concentrate and retain information. Regular marijuana use has been shown to be associated with cognitive deficits and poor academic performance. This may be especially problematic during teens' peak learning years, when their brains are still developing.
  • One study found an association between an increase in adolescent marijuana use and a decrease in the likelihood of attaining at least a high school education.
  • Research found that youths with an average grade of "D" or below were more than four times as likely to have used marijuana in the past year as youths who reported an average grade of "A."10
  • Students who have smoked marijuana within the past year are more than twice as likely to cut class than those who did not smoke, and health problems associated with using marijuana can keep students from attending school due to illness.

Marijuana's other dangers.

  • The substances in marijuana stay in the fatty parts of the body for long periods of time.
  • A 50% concentration of THC can be found in the body up to eight days after using marijuana and traces can be found in the body up to 3 months after use . THC, the active ingredient in marijuana, accumulates particularly in the testes, liver and brain of users.
  • PET scans (a brain mapping method which allows scientists to visualize what is happening in the brain) of regular marijuana users show that marijuana may continue to impact the brain three or more days after use, particularly affecting motor coordination, memory and learning. According to two studies, marijuana use narrows the arteries in the brain, “similar to patients with high blood pressure and dementia”11 and may explain why memory tests are difficult for marijuana users. In addition, “chronic consumers of cannabis lose molecules called CB1 receptors in the brain’s arteries,”12 leading to blood flow problems in the brain which can cause memory loss, attention deficits, and impaired learning ability.
  • Research has now established that marijuana is addictive. Each year, more teens enter treatment with a primary diagnosis of marijuana dependence than for all other illicit drugs combined. Over sixty percent of teens admitted to drug treatment cite marijuana as their primary substance of abuse.
  • Research also shows that marijuana use is three times more likely to lead to dependence among adolescents than among adults.
  • Research indicates that the earlier kids start using marijuana, the more likely they are to become dependent on this or other illicit drugs later in life.
  • The proportion of admissions for primary marijuana abuse increased from 6% in 1992 to 64% percent of admissions in 2002. Almost half (46 percent) of the people admitted for marijuana were under 20 years old. Of those admitted for treatment for primary marijuana dependence, 56 percent had first used the drug by age 14, and 26 percent had begun by age 12.
  • Even marijuana proponents acknowledge that marijuana use is harmful for teens. Allen St. Pierre, the executive director of NORML (National Organization for the Reform of Marjuana Laws) recently stated that "One can argue before a young person reaches full brain development in their early 20's, they should not use or have legal access to marijuana."1
  • Scientists have proven that marijuana users experience changes in the flow of blood to their brains. Ronald Herning of the National Institute on Drug Abuse (NIDA) found that marijuana smokers may suffer from narrowed blood vessels in their brains, possibly explaining why smokers experience memory and thinking problems.12


Source Information

1Ana Shen, "Is Marijuana Really Harmless?," The Ledger, January 3, 2005

2Brent A. Moore, PhD, Erik M. Augustson, PhD, MPH, Richard P. Moser, PhD, and Alan J. Budney, PhD, "Respiratory Effects of Marijuana and Tobacco Use in a U.S. Sample," Journal of General Internal Medicine, December 2004

3Steve Boggan, "If cannabis is safe, why am I psychotic?," The Times of London, January 2004

4"Kids and Cannabis," The Times of London, February 2005

5"Cannabis Raises Risk of Pyschosis," BBC News, December 2004

6"White House Drug Czar Launches Campaign to Stop Drugged Driving.” Office of National Drug Control Policy Press Release, November 2002.

7Stephanie Blows, Rebecca Q. Ivers, Jennie Connor, Shanthi Ameratunga, Mark Woodward & Robyn Norton, "Marijuana Use and Car Crash Injury," Addiction, Vol 100, April 2005

8Department of Health and Human Services, Substance Abuse and Mental Health Services Administration, Office of Applied Studies. “Marijuana Use and Delinquent Behaviors and Youths.” The NSDUH Report. 9 January 2004

9Department of Health and Human Services, Substance Abuse and Mental Health Services Administration, Office of Applied Studies, 2001 National Household Survey on Drug Abuse, September 2002

10Marijuana Use Negatively Impacts Teen Learning and Academic Success, Experts Say” PR Newswire. 7 October 2004.

11"Marijuana Affects Brain Long-Term, Study Finds" Reuters, February 7, 2005

12"Marijuana affects blood vessels," BBC News, February 2005