Low to moderate marijuana use didn’t affect lungs

Smoking low levels of marijuana over decades does not harm lung function, according to a study led by researchers from the University of California-San Francisco.

More than 5,000 men and women between the ages of 18 and 30 were recruited in 1985 and 1986 and went to an average of four medical exams over 20 years. They were asked at each about current and past smoking habits for tobacco and marijuana.

The volume and force of their breath were measured with spirometry devices.

As expected, tobacco use was associated with a decline in lung function. That wasn’t the case for marijuana use, which was measured in “joint-years,’’ each equivalent to smoking 365 joints or filled pipe bowls.

Within seven joint-years – the equivalent of having a joint a day for seven years or one per week over 49 years – there was no evidence that an increase in marijuana exposure negatively affected lung function, the authors wrote. They noted that people who were heavier users may have experienced negative effects.

BOTTOM LINE: Low to moderate marijuana use did not hurt lung function among study participants.

CAUTIONS: The study included few people who were heavy marijuana users, and even fewer who were not also tobacco smokers. Marijuana and tobacco use was self-reported, meaning researchers relied on participants to recall their habits.

WHERE TO FIND IT: Journal of the American Medical Association, Jan. 11