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Table 1.  

Study (year) Study
Results Ref.
Hancox et al.
919 Increased lung capacity and airway
resistance in marijuana smokers. No
evidence of airway obstruction, gas
trapping or impaired gas transfer
Tan et al.
878 Marijuana smoking not associated
with increased bronchitic symptoms
and COPD.
Sherrill et al.
856 Pulmonary function was reduced
in subjects reporting
marijuana smoking
Tashkin et al.
394 No effect of marijuana smoking on
FEV1 decline
et al. 2007
339 Marijuana associated with airflow
obstruction, hyperinflation and
large airways impairment
Bloom et al.
990 No effect of marijuana on FEV1
or FVC
60 No difference between marijuana
smokers and controls
et al. (1981)
23 Normal spirometry in
marijuana smokers
Moore et al.
6728 marijuana use not associated with
decreased FEV/FVC ratio
et al. (1991)
63 No significant difference in
FEV/FVC and DLco in marijuana
smokers and nonsmokers
Tashkin et al.
189 Marijuana smokers had lower sGaw
compared with controls (p < 0.001)
Tashkin et al.
542 Marijuana smoking associated with
airway hyper-responsiveness with
lose-dose methacholine
Tilles et al.
68 Marijuana smoking regardless of
tobacco smoking, resulted in
reduction of single breath DLco
compared with nonsmokers
Tashkin et al.
446 Male marijuana smokers had
reduced sGaw compared with male
tobacco smokers. No difference
in DLco.
Total:   12,613  

Epidemiological Associations Between Cannabis Use and Lung Function.

Taylor et al. performed two studies (2000 [8] and 2002 [19]) on the same cohort that have been superseded by Hancox et al. 2010 [18].
COPD: Chronic obstructive pulmonary diease; DLco: Diffusing capacity for carbon monoxide; FEV1: Forced expiratory volume; FVC: Forced vital capacity; sGaw: Specific airway conductance.

Table 2.  

Results Ref.
Beshay et al.
17 27 53 Upper lobe predominance
with bullae ranging from 0.3
to 12 cm
et al. (2000)
4 38 NS All had upper lobe bullae
and normal lower lobes.
Gao et al.
1 23 NS Bilateral upper lobe bullae,
more prominent on the right
Hii et al.
10 41 74 Upper and mid-zone
emphysematous bullae
Phan et al.
1 26 >10 Extensive cystic and bullous
lung changes primarily
affecting lower lobes
et al. (2002)
3 39 NS Large apical lung bullae [44]

Reports of Bullous Lung Disease in Cannabis Users.

NS: Not stated.

Table 3.  

Measure Cannabis Tobacco
FEV1 ↔/↓
FVC ↑↑
FEV/FVC ratio ↓↓
TLC ↑↑ ↔/↑
RV ↑↑ ↑↑
sGaw ↔/↓↓

Differences in Lung Function Associated With Cannabis and Tobacco Use.

: No association; : Increase; : Decrease; DLco: Diffusing capacity for carbon
monoxide; FEV1: Forced expiratory volume; FVC: Forced vital capacity;
RV: Residual volume; sGaw: Specific airway conductance; TLC: Total
lung capacity.
Data taken from [18].


Effects of Smoking Cannabis on Lung Function

  • Authors: Robert J. Hancox, MD; Marcus H.S. Lee, MD
  • CME Released: 8/22/2011
  • Valid for credit through: 8/22/2012
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Target Audience and Goal Statement

This activity is intended for primary care physicians, pulmonary medicine specialists, and other physicians who care for individuals who use cannabis.

The goal of this activity is to evaluate the effects of cannabis on lung function and the risk for cancer.

Upon completion of this activity, participants will be able to:

  1. Distinguish short-term effects of smoking cannabis on lung function
  2. Evaluate the long-term effects of cannabis use on lung function
  3. Describe the effects of cannabis use in promoting emphysema and lung bullae
  4. Analyze the effects of cannabis use on the risk for cancer


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  • Robert J. Hancox, MD

    Department of Respiratory Medicine, Waikato Hospital, Hamilton, New Zealand; Department Preventive & Social Medicine, University of Otago, Dunedin, New Zealand


    Disclosure: Robert J. Hancox, MD, has disclosed no relevant financial relationships.

  • Marcus H.S. Lee, MD

    Department of Respiratory Medicine, Waikato Hospital, Hamilton, New Zealand


    Disclosure: Marcus H.S. Lee, MD, has disclosed no relevant financial relationships.


  • Elisa Manzotti

    Editorial Director, Future Science Group, London, United Kingdom


    Disclosure: Elisa Manzotti has disclosed no relevant financial relationships.

CME Author(s)

  • Charles P. Vega, MD

    Associate Professor; Residency Director, Department of Family Medicine, University of California, Irvine


    Disclosure: Charles P. Vega, MD, has disclosed no relevant financial relationships.

CME Reviewer(s)

  • Nafeez Zawahir, MD

    CME Clinical Director, Medscape, LLC


    Disclosure: Nafeez Zawahir, MD, has disclosed no relevant financial relationships.

  • Sarah Fleischman

    CME Program Manager, Medscape, LLC


    Disclosure: Sarah Fleischman has disclosed no relevant financial relationships.

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Effects of Smoking Cannabis on Lung Function: Cannabis & Bronchitis


Cannabis & Bronchitis

Numerous studies confirm that smoking cannabis can lead to respiratory symptoms. These studies show that cough, increased sputum production and wheeze are present in approximately a fifth to a third of cannabis smokers.[9–11] Cannabis smoking is also associated with dyspnoea, pharyngitis, hoarsening of voice and exacerbations of asthma.[10] These symptoms appear to result from the toxic effects of cannabis smoke on the bronchial mucosa. Bronchoscopic mucosal biopsies from 40 cannabis-only smokers and 31 tobacco-only smokers have demonstrated that both cannabis and tobacco smoking cause significant bronchial damage, with an increase in basal cell hyperplasia, goblet cell hyperplasia, cell disorganization, nuclear variation, and an increase in nuclear/cytoplasm ratio.[12] This study also demonstrated an increase in squamous cell metaplasia in cannabis smokers, raising the possibility that smoking cannabis may be a risk factor for developing lung cancer.

Another report found that even asymptomatic cannabis smokers with normal physical examinations and spirometric function have central airway inflammation under direct bronchoscopic visualization, bronchial mucosal biopsies and bronchial lavage fluid.[13] Those who smoked both cannabis and tobacco also had distal airway inflammation. There was a high incidence of erythema, edema and airway secretions in both exclusive cannabis smokers and exclusive tobacco smokers. These findings demonstrate that routine physical examination and spirometry may be insensitive measures of lung injury caused by cannabis. While the finding that cannabis smoke causes mucosal damage is not surprising, the most striking result of this study was the fact that cannabis smokers with an average of a few joints a day had the same degree of airway damage as tobacco smokers of 20–30 cigarettes a day. Moreover, this damage was present in young and asymptomatic cannabis smokers.