Marijuana Unlikely to Cause Head, Neck, or Lung Cancer
May 8, 2000 (Boston) -- Marijuana, unlike tobacco and alcohol, does not
appear to cause head, neck, or lung cancer, says a researcher from Johns
Hopkins Medical School in Baltimore who presented findings from a study here
recently at a meeting of internal medicine physicians.
There has been an ongoing debate about whether marijuana is as dangerous as
tobacco in terms of cancer development. Daniel E. Ford, MD, tried to sort out
the evidence by the lifestyles -- including marijuana, tobacco, and alcohol use
-- of 164 persons who were newly diagnosed with head, neck, or lung cancer
compared to a group of 526 healthy persons living in the same area. The average
age of patients was 49, while the average age of the healthy volunteers was 44.
The cancer patients were all treated at four Baltimore-area hospitals, and the
"controls" (healthy comparison group) were selected from a large group
of people living in the Baltimore area who had been participating in an ongoing
study. Ford tells WebMD that he wanted to find out whether the cancer patients
were more likely to smoke marijuana or tobacco or to drink than were the
According to Ford, he thought he would find an association between marijuana
use and cancer, but "that the association would fall away when we corrected
for tobacco use. That was not the case. The association was never there."
And that surprised him because of the way marijuana is smoked: deep
inhalations, with the smoke held in for effect. "It seemed natural that
there would be some connection," he tells WebMD.
Based on these findings, Ford says that cancer prevention efforts should
"remain focused on tobacco and alcohol, two known carcinogens."
He says his conclusions differ from another study reported recently. That
study linked marijuana use to cancer, but Ford says he thinks the difference
can be explained by the fact that the healthy volunteers in that study "had
very, very low use of marijuana." That contrasts to his study, in which
"we were investigating the effect of marijuana as it is commonly used in
the community," he says. Use of all substances -- tobacco, alcohol, and
marijuana -- was common among both cancer patients and controls, he says.
"We attempted to assess both lifetime and current use of
substances," he says. Participants were also asked to differentiate between
use of marijuana cigarettes, marijuana pipes, or consumed marijuana.
Distinctions were also made between weekend and weekday use of marijuana, he
"Ever use of marijuana was 66% among controls and 60% among the
cases," he says. "Daily marijuana use for a month or more was not
associated with increased risk, nor was age at first use, depth of inhalation,
or use of a pipe." Surprisingly, using marijuana was not associated with
increased cancer risk, even among those who never used tobacco, he says.