Smoking up to a joint per day doesn't seem to decrease lung function, according to a study published in Jan. 11 edition of Journal of the American Medical Association.
In fact, occasional marijuana use
was associated with slightincreases
in lung airflow rates and increases
in lung volume, the study found.
Far from a license to light up, the study eases the worry among some health professionals that daily use of marijuana for medical reasons
could have negative, long-term implications on pulmonary health.
The study, led by Mark Pletcher of the University of California, San Francisco, compared the effects of both cigarette and marijuana smoking over a period of 20 years in a group of more than 5,000 adults
, part of a longitudinal study called Coronary Artery Risk Development in Young Adults (CARDIA).
The data revealed nothing new about tobacco: As exposure to tobacco
goes up, lung capacity in terms of the amount of air a smoker can exhale goes down. It's a linear relationship.
Not so with marijuana. More pot smoking was associated with increases in lung capacity up to a level equivalent to about one joint per day for seven years or one joint per week for up to 49 years. Only at levels of marijuana smoking higher than this did the researchers see a leveling off and then potential reversal of this relationship to improved lung capacity.