Pot Smoking Not Linked to Lung Cancer
Study Shows No Increased Risk for Even the Heaviest Marijuana Smokers
WebMD News Archive
May 23, 2006 -- People who smoke marijuana do not appear to be
at increased risk for developing lung
cancerlung cancer, new research
While a clear increase in cancercancer risk was seen among cigarette smokers in
the study, no such association was seen for regular cannabis users.
Even very heavy, long-term marijuana users who had smoked more than 22,000
joints over a lifetime seemed to have no greater risk than infrequent marijuana
users or nonusers.
The findings surprised the study’s researchers, who expected to see an
increase in cancer among people who smoked marijuana regularly in their
“We know that there are as many or more carcinogens and co-carcinogens in
marijuana smoke as in cigarettes,” researcher Donald Tashkin, MD, of UCLA’s
David Geffen School of Medicine tells WebMD. “But we did not find any evidence
for an increase in cancer risk for even heavy marijuana smoking.” Carcinogens are substances that cause
Tashkin presented the findings today at The American Thoracic Society’s
102nd International Conference, held in San Diego.Boomers Reaching
The study population was limited to people who were younger than 60 because
people older than that would probably not have used marijuana in their teens and early adult years.
“People who may have smoked marijuana in their youth are just now getting to
the age when cancers are being seen,” Tashkin says.
A total of 611 lung cancer patients living in Los Angeles County, and 601
patients with other cancers of the head and neck were compared with 1,040
people without cancer matched for age, sex, and the neighborhood they lived
All the participants were asked about lifetime use of marijuana, tobacco,
and alcohol, as well as other drugs, their diets, occupation, family history of
lung cancer, and socioeconomic status.
The heaviest marijuana users in the study had smoked more than 22,000
joints, while moderately heavy smokers had smoked between 11,000 and 22,000
While two-pack-a-day or more cigarette smokers were found to have a 20-fold
increase in lung cancer risk, no elevation in risk was seen for even the very
heaviest marijuana smokers.
The more tobacco a person smoked, the greater their risk of developing lung
cancer and other cancers of the head and neck. But people who smoked more
marijuana were not at increased risk compared with people who smoked less and
people who didn’t smoke at all.
The THC Connection
Studies suggest that marijuana smoke contains 50% higher concentrations of
chemicals linked to lung cancerlung cancer than cigarette smoke. Marijuana
smokers also tend to inhale deeper than cigarette smokers and hold the inhaled
smoke in their lungs longer.
So why isn’t smoking marijuana as dangerous as smoking cigarettes in terms
of cancercancer risk?