What is Marijuana?

Marijuana is a drug made from the dry, shredded parts of the Cannabis sativa hemp
plant.  It is usually smoked in hand-rolled cigarettes called joints, in pipes, or in water
pipes called bongs. It is also smoked in blunts, which are hollowed-out cigars filled with
a mixture of tobacco and marijuana.

Marijuana contains a potent chemical called delta-9-tetrahydrocannabinol, more
commonly known as THC. It’s very similar to chemicals that the brain naturally produces,
and disrupts the function of these chemicals in the brain.

Marijuana today is more potent than marijuana of past decades. For a long time THC
levels averaged 2.3 percent. Today, average THC levels are higher than 8 percent and
can go up to 35 percent in medical marijuana.

Can Marijuana Be Medicine?

The FDA has not approved the medicinal use of marijuana because there is not enough
evidence showing that the benefits of its use outweigh the risks. Also, medicine requires
consistent doses, while each marijuana plant can have very different levels of THC and
other compounds. The FDA has approved some THC-based drugs, which are prescribed
to treat pain and nausea.

Marijuana has also only been shown to be useful for a limited number of conditions or
symptoms, compared with the wide variety for which its use is promoted. In addition, it
may not even be as effective as other drugs approved by FDA for treatment of the
same symptoms.

Research has mostly assessed the health effects of marijuana use among healthy
individuals. Individuals interested in using marijuana medicinally may be at higher risk
for health effects from it due to the very conditions for which they seek treatment. This
is because many chronic or serious conditions, such as cancer or AIDS, are associated
with a greater risk of other diseases or health problems.

Tobacco vs. Marijuana

Like tobacco smoke, marijuana smoke contains cancer-causing chemicals.  There are
33 cancer-causing chemicals contained in marijuana. Marijuana smoke also deposits tar
into the lungs. In fact, when equal amounts of marijuana and tobacco are smoked,
marijuana deposits four times as much tar into the lungs. This is because marijuana
joints are un-filtered and often more deeply inhaled than cigarettes.

Marijuana and the Lungs

Marijuana smoke is also an irritant to the lungs, and frequent marijuana smokers can
have many of the same respiratory problems experienced by people who smoke
tobacco. These include coughing and phlegm production on most days, wheezing,
bronchitis, and greater risk of lung infection, although most of these may go away
after stopping smoking marijuana. Frequent marijuana smokers also have more
healthcare visits both overall and for respiratory conditions compared to nonsmokers.
While research has not shown a clear increase in risk for lung cancer among marijuana
smokers, results have been mixed for heavy, long term use.

Smoking marijuana may be associated with the formation of large air sacs in the lung,
called bullae, which can lead to shortness of breath and, if they rupture, death. Similarly,
there are reports of sudden lung collapse or air pockets forming between the lungs
among marijuana smokers.

Other Health Effects of Marijuana

Marijuana has many effects on the brain. It impairs short-term memory and motor
coordination; slows reaction time; alters mood, judgment and decision-making; and in
some people can cause severe anxiety or loss of touch with reality. Because of these
effects, marijuana use more than doubles a driver’s risk of being in an accident.

Marijuana also affects the heart. The heart rate is raised 20-100 percent shortly
after smoking, an effect which can last up to 3 hours and put users at an increased
risk of heart attack.

Marijuana use can affect the general quality of the user’s life as well. Heavy marijuana
users generally report lower life satisfaction, poorer mental and physical health,
relationship problems and less academic and career success compared to their peers.

Youth and Marijuana

Marijuana use is particularly harmful to youth since the part of the brain that craves
pleasure matures earlier than the area that controls our ability to understand risks
and consequences. A national study by Monitoring the Future showed that in 2013
1.1% of 8th graders, 4.0% of 10th graders, and 6.5% of 12th graders reported
using marijuana daily.

Marijuana is highly accessible, especially to older teenagers. In 2013, 39.1% of
8th graders, 69.7% of 10th graders, and 81.4% of 12th graders reported marijuana
as being fairly easy or very easy to get. Studies show that as availability increases,
perception of harm decreases.

The perception that there is no great risk in smoking marijuana is decreasing among
youth. In 2013, 61.0% of 8th graders, 46.5% of 10th graders and 39.5% of 12th
graders said there was a great risk in smoking marijuana regularly. These numbers
had been steadily declining over the last five to eight years.

Is it Addictive?

Marijuana is often thought to not be addictive. However, about 9% of those who try
marijuana will become addicted. Youth are more likely than adults to become addicted
to marijuana. About 2.7 million people in the U.S. meet clinical criteria for
marijuana dependence.

THC stimulates brain cells to release the chemical dopamine, which creates a euphoric
feeling and can lead to a physical addiction. Similar to tobacco withdrawal, people trying
to quit marijuana report irritability, sleeping difficulties, craving, and anxiety.

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Download our Marijuana Pamphlet, "Questions about Marijuana?" HERE.


Johnston, L. D., O’Malley, P. M., Bachman, J. G., & Schulenberg, J. E. (2013). Monitoring the Future national results on adolescent drug use: Overview of key findings, 2012. Ann Arbor: Institute for Social Research, The University of Michigan. Retreived from

Matthias, P., Tashkin, D. P., Marques-Magallanes, J. A., Wilkins, J. N., & Simmons, M. S. (1997). Effects of Varying Marijuana Potency on Deposition of Tar and Δ< sup> 9-THC in the Lung During Smoking. Pharmacology Biochemistry and Behavior, 58(4), 1145-1150. Retreived from

National Institute on Drug Abuse. (July 2012). DrugFacts: Is Marijuana Medicine? Retrieved February 18, 2013, from

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Thurstone, C. Understand the Big Deal: How Marijuana Harms Youth. Retrieved February 18, 2013, from

Tomar, Rajpal C.; Beaumont and Hsieh (August 2009) (PDF), Evidence on the carcinogenicity of marijuana smoke, Reproductive and Cancer Hazard Assessment Branch Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, retrieved 24 January 2013 from