Modest Marijuana Exposure Does Not Adversely Affect Pulmonary Function, but High Cumulative Exposure Does
Previous investigations have not shown a consistent impact of marijuana smoking on pulmonary function. Investigators conducted a longitudinal analysis of 5016 adults* enrolled in the CARDIA† study to assess the impact of marijuana exposure on pulmonary function (FEV1 and FVC). Marijuana exposure was assessed at 6 follow-up exams, permitting calculation of “joint-years” (where 365 joints=1 joint-year) and tobacco pack-years. Fifty-six percent of participants (n=2807) attended the 20-year follow-up examination without differential attrition by marijuana use.
- In adjusted analyses, the association between marijuana use and pulmonary function was nonlinear:
- at low lifetime exposure, marijuana use was associated with increased FEV1 and FVC.
- at >7 joint-years, the positive association shown between marijuana use and pulmonary function leveled off.
- at >10 joint-years, there was a nonsignificant decline in FEV1.
- at >20 episodes of marijuana use per month, the decline in FEV1 was significant.