New Zealand study shows.
The researchers included Richard Beasley, MBChB, of the Medical Research
Institute of New Zealand in Wellington.
They studied 339 New Zealand adults, including 75 people who only smoked
pot, 91 who smoked pot and tobacco, 92 who only smoked tobacco, and 81 who
didn't smoke pot or tobacco.
Participants took lung function tests, urine tests, got high-tech lung scans
using CTB scanning, and
completed surveys about their smoking habits.
All of the pot smokers had regularly smoked marijuana for at least five
years. All of the tobacco smokers had smoked cigarettes for at least one year.
Their urine tests confirmed their use of tobacco or marijuana.
Pot is illegal in New Zealand, so participants were promised total
anonymity. Those who used other illegal drugs were excluded from the study.
Beasley's team wanted to find out whether long-term marijuana use was, like
tobacco, associated with increased risk of emphysema. It wasn't.
However, long-term marijuana use was linked to lung problems including
coughing, wheeze, chest tightness, and airflow obstruction.
Beasley's team calculates that, in terms of airflow obstruction, one
marijuana joint equaled the effect of smoking 2.5 to five cigarettes at once.
The finding is "of major public health significance," write the
The results are likely due to differences between tobacco cigarettes and
marijuana joints, note the researchers.
"Cannabis is usually smoked without a filter and to a shorter butt
length, and the smoke [has] a higher temperature," write Beasley and
colleagues, adding that people inhale deeper and hold their breath longer when
The study appears in the advance online edition of the journal
By Miranda Hitti
Reviewed by Louise Chang
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