Cannabis and lung disease

• gaseous and the particulate phases of tobacco and cannabis smoke contain a similar range of harmful chemicals
  • however, differing patterns of inhalation mean that smoking a 'joint' of cannabis results in exposure to significantly greater amounts of combusted material than with a tobacco cigarette
  • histopathological effects of cannabis smoke exposure include changes consistent with acute and chronic bronchitis
  • cellular dysplasia has also been observed, suggesting that, like tobacco smoke, cannabis exposure has the potential to cause malignancy
  • symptoms of cough and early morning sputum production are common (20-25%) even in young individuals who smoke cannabis alone
  • almost all studies indicate that the effects of cannabis and tobacco smoking are additive and independent
  • in 2002, the British Lung Foundation published a report entitled Cannabis — a smoking gun? In summary, this report found that three or four cannabis cigarettes a day are associated with the same evidence of acute and chronic bronchitis and the same degree of damage to the bronchial mucosa as 20 or more tobacco cigarettes a day
  • cannabis smoking is associated with bullous lung disease in young people - it has also been noted that (2):
    • inflammatory lung changes, chronic cough, and chest infections are similar to those in cigarette smokers, but may also be commoner in younger people
    • premalignant changes have been shown in the pulmonary epithelium, and there are reports of lung, tongue, and other cancers in cannabis smokers

Cannabis and lung cancer

• a cohort study found that “heavy” cannabis smoking was significantly associated with more than a twofold risk (hazard ratio 2.12, 95 % CI 1.08–4.14) of developing lung cancer over the 40-year follow-up period, even after statistical adjustment for baseline tobacco use, alcohol use, respiratory conditions, and socioeconomic status (3)
• a growing number of studies report an independent association of cannabis smoking with the development of lung cancer (4)

Reference:

1. Intern Med J. 2003;33(7):310-3.
2. BMJ. 2003;326(7396):942-3.
3. Callaghan, R.C et al. Marijuana use and risk of lung cancer: a 40-year cohort study. Cancer Causes Control 2013; 24:1811–1820
4. KhoJ L et al. Effects of cannabis smoking on the respiratory system: A state-of-the-art review. Respir Med. 2024 Jan;221:107494.