The effects of marijuana exposure on expiratory airflow. A study of adults who participated in the U.S. National Health and Nutrition Examination Study

Ann Am Thorac Soc. 2015 Feb;12(2):135-41. doi: 10.1513/AnnalsATS.201407-333OC.


Rationale: Given the inconclusive science on the long-term effects of marijuana exposure on lung function, the increasing tetrahydrocannabinol composition of marijuana over time, and the increasing legal accessibility of the substance, continued investigation is needed.

Objectives: To determine the independent association between recent and chronic marijuana smoke exposure with spirometric parameters of lung function and symptoms of respiratory health in a large cohort of U.S. adults.

Methods: This is a cross-sectional study of U.S. adults who participated in the National Health and Nutrition Examination Survey cycles from 2007-2008 and 2009-2010, using the data from standardized spirometry and survey questions performed during these years.

Measurements and main results: In the combined 2007-2010 cohort, 59.1% replied that they had used marijuana at least once, and 12.2% had used in the past month. For each additional day of marijuana use in the prior month, there were no changes in percent predicted FEV1 (0.002 ± 0.04%; P = 0.9), but there was an associated increase in percent predicted FVC (0.13 ± 0.03%, P = 0.0001) and decrease in the FEV1/FVC ratio (-0.1 ± 0.04%; P < 0.0001). In multivariable regressions, 1-5 and 6-20 joint-years of marijuana use were not associated with an FEV1/FVC less than 70% (odds ratio [OR] = 1.1, 95% confidence interval [CI] = 0.7-1.6, P = 0.8, and OR = 1.2, 95% CI = 0.8-1.8, P = 0.4, respectively), whereas over 20 joint-years was associated with an FEV1/FVC less than 70% (OR = 2.1; 95% CI = 1.1-3.9; P = 0.02). For each additional marijuana joint-year smoked, there was no associated change in the mean percent predicted FEV1 (0.02 ± 0.02%; P = 1.00), an increase in percent predicted FVC (0.07 ± 0.02%; P = 0.004), and a decrease in FEV1/FVC (-0.03 ± 0.01%; P = 0.02).

Conclusions: In a large cross-section of U.S. adults, cumulative lifetime marijuana use, up to 20 joint-years, is not associated with adverse changes in spirometric measures of lung health. Although greater than 20 joint-years of cumulative marijuana exposure was associated with a twofold increased odds of a FEV1/FVC less than 70%, this was the result of an increase in FVC, rather than a disproportional decrease in FEV1 as is typically associated with obstructive lung diseases.

Keywords: cannabis; marijuana smoking; obstructive lung disease.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adolescent
  • Adult
  • Cohort Studies
  • Cross-Sectional Studies
  • Female
  • Forced Expiratory Volume / physiology
  • Humans
  • Lung / physiopathology*
  • Lung Diseases, Obstructive / physiopathology
  • Male
  • Marijuana Smoking / physiopathology*
  • Middle Aged
  • Multivariate Analysis
  • Nutrition Surveys
  • Regression Analysis
  • Spirometry
  • United States
  • Vital Capacity / physiology
  • Young Adult