A Longitudinal Study of Cannabis Use Increasing the Use of Asthma Medication in Young Norwegian Adults

Jørgen G. Bramness; Tilmann von Soest


BMC Pulm Med. 2019;19(52) 

In This Article


Bronchial asthma is a common long-term inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include episodes of wheezing, coughing, chest tightness and shortness of breath and are often symptomatically diagnosed and treated with broncho-dilatators and/or steroids for inhalation.

Known risk factors for bronchial asthma are family history of asthma, allergies, respiratory infections,[1] environmental pollutions (including dust mite[2] and air pollution[3]), tobacco smoking[4] and obesity.[5] Some studies also find female gender to be a risk factor.[6]

The recent changes in attitude towards cannabis use, where the drug is perceived as almost harmless,[7] and recent changes in legislation regulating its use, especially in the US, may increase the risk of asthma from increased cannabis use.[8] Greater awareness of the possible negative consequences of cannabis use would be prudent. Since cannabis, despite the development of novel ways of use, is most often smoked as marijuana by itself or as hashish together with tobacco, there is concern that its use might inflict respiratory consequences.[9]

Cannabis users seem to have an increased risk of chronic bronchitis,[10] reporting signs like coughing, sputum and wheezing, but no more shortness of breath.[11–13] A feared long-term negative consequence of chronic bronchitis is chronic obstructive pulmonary disorder (COPD),[14] but current research suggests that the use of cannabis does not increase the risk of COPD.[15,16]

Another consequence of cannabis smoking could be bronchial asthma. Three lines of research have been followed in this context. Firstly, some studies have investigated the potential acute bronchodilator effects of cannabis. Several older studies have shown a significant positive airway effect on bronchial asthma of cannabis administered in different ways to both healthy volunteers and asthmatic patients.[10,17–21] Secondly, some cases have been observed where allergy to some components of cannabis seems to precipitate asthma.[22,23] Thirdly, several larger population studies found an increase in symptoms of bronchial asthma in cannabis users: Several US cross-sectional health surveys have found more bronchial asthma among users of cannabis compared to others, even after controlling for age, gender, and tobacco use.[13,16,24] Moreover, three publications from the longitudinal Dunedin birth cohort study initially found an effect on asthma among all cannabis users, but when controlling for several confounders only found the association in women.[25] Results from the study also showed a positive effect on asthma from quitting cannabis.[26] Most population studies control for gender and tobacco use,[13,16,24–27] some by analysing the effect only in non-users of tobacco.[24] Some even control for previous asthma,[16,25,27] but few if any control for being overweight or for the presence of allergies. Overall the studies together suggest that there is an association of cannabis with bronchial asthma,[28] with an overall effect a little less than for tobacco smokers.[13] Still, there are a limited number of studies investigating the relationship between cannabis use and bronchial asthma while controlling for a variety of potential covariates, and further studies are therefore needed.[9] We have found no studies with the prescriptions for asthma medication as outcome measure.

In Norway cannabis is mostly consumed as hashish, the resin of cannabis, prepared and mixed with tobacco and inhaled in cigarettes or joints. It is therefore important to control for tobacco smoking when investigating the possible effects of cannabis on the use of drugs for bronchial asthma.

In this longitudinal study we investigated the relationship between self-reported cannabis use and future filling of prescriptions for inhaled bronchodilators or steroids for the treatment of bronchial asthma, taking into consideration age, gender, weight, smoking and asthma and allergies.