The Impact of Marijuana

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Policy Statement of the American Academy of Pediatrics
Reprinted in Pediatrics, October 1999 and AAP News, October 1999
Available free at or for $5 at (847) 981-7904

Many adults of the baby boomer generation (including youth workers) have ambivalent feelings about the numerous, well-publicized reports that the use of marijuana by young people increased dramatically in the 1990s. Many are unaware that the marijuana of today is much different from the drug of a generation ago, and that there is growing research evidence of the harmful effects of the drug.

The American Academy of Pediatrics recently released a policy statement that concludes that the use of marijuana by adolescents is a "major health problem" and that pediatricians should "counsel young people against any use of the drug." The statement also concludes that marijuana is addictive, and that teenagers who are dependent on the drug should be offered treatment options "rather than simply punishment."

Many adults who smoked marijuana in high school or college are unaware that the potency has changed dramatically as a result of selective breeding of plants. A study of the potency of street samples, measured in terms of the concentration of THC, found a 500 percent increase between 1975 and 1997. The lower potency in the 1960s and 1970s was compatible with "self-experimentation," whereas the higher potency is believed to result in more compulsive use in recent years.

In addition to the impaired problem-solving skills of those "under the influence," regular users also have impaired short-term memory, learning and attention spans even up to six weeks after the discontinuation of use. Because it impairs judgment and coordination, it "contributes substantially" to automobile crashes and other accidents. The statement also describes the evidence of marijuana as a "gateway" drug that tends to progress to "harder" drugs.

Marijuana has an impact on physical health as well. Smoking marijuana increases the heart rate and causes small increases in blood pressure, neither of which is dangerous to healthy adolescents. In contrast, the risk of cancer and other long-term effects on the lungs (even with less potent marijuana) are similar to smoking tobacco. The policy statement does not include the most recent research findings indicating increased risk of cancers of the mouth, throat and larynx, based on a study conducted at New York's memorial Sloan-Kettering Cancer Center.

In addition, the policy statement warns that "heavy marijuana use may be especially dangerous for adolescents during puberty" because it causes changes such as decreased sperm counts, decreased testosterone and irregular ovulation. Infants born to mothers who smoke marijuana during pregnancy are shorter, weigh less and have smaller heads. However, it is not clear from the statement whether there are serious reproductive risks to adolescents who are using birth control or trying to avoid pregnancy.