Cannabis A groundbreaking 20-year study investigated the links between tobacco, cannabis and lung function, and found that while tobacco caused adverse effects, cannabis did not. As a result of this study and others like it, healthcare is beginning to pay attention, and health insurers are even starting to cover medical cannabis costs!
In 2012, a groundbreaking scientific study (Association Between Marijuana Exposure and Pulmonary Function Over 20 Years, Pletcher MJ et al.) was published on the effects of cannabis smoke on lung function compared to that of tobacco smoke.
The study followed thousands of subjects for twenty years in order to build up a full picture of potential associations, unlike many studies that simply look at a brief window in time and are therefore unable to prove causation, even if they demonstrate correlation.
Although several years have passed since its publication, this study remains one of the most rigorous and reliable of the existing studies comparing cannabis and tobacco, and has proved to be very influential. Recently, two Canadian life insurance companies stated that they would henceforth cease to class cannabis smokers in the same high-risk category as tobacco smokers, stating that current research showed no evidence of any “long-term risk of cancer or anything equivalent to tobacco”.
In this article, we will take an in-depth look at the findings of the study and other related studies that have been published since then, and discuss the practical changes these findings have brought about within the industry.
What Did The Study Investigate?
It is well-known that cannabis smoke contains many of the same compounds present in tobacco smoke, but the question of whether or not the two are equally damaging has caused controversy for years. Prior studies that have investigated the effects of cannabis smoke have found that it can cause inflammation and damage to the mucous membranes of the lungs, as well as related symptoms such as coughing, increased phlegm production, and wheezing – all of which are also found in tobacco smokers.
On the other hand, studies into long-term lung function and disease associated with cannabis use have failed to find any clear-cut link. Therefore, this study aimed to clear up the confusion once and for all. Cannabis is of increasing importance in healthcare throughout the world, and users are increasing with every year, as its legitimacy increases. Thus, getting the facts straight is crucial for our understanding of cannabis and how to incorporate it into clinical practice.
Over the course of more than two decades (March 1985 – August 2006), the study followed upwards of five thousand participants, tracking their cannabis use, tobacco use, and pulmonary function. The study measured current habits and estimated lifetime cumulative exposure to both types of smoke, and looked for associations.
How Was The Data Collected?
The data was collected as part of the Coronary Artery Risk Development in Young Adults (CARDIA) study, which has been gathering data since 1985 and is expected to conclude in 2018. CARDIA aims to study variables such as race, height, waist circumference, smoking habits, and secondhand smoke exposure, to identify risk factors for heart disease.
Thus, CARDIA randomly selected 5,115 participants from the two largest racial groups (White, not Hispanic, and Black, not Hispanic), sampled from four U.S. communities. Participants were aged 18 – 30 years and healthy at time of enrollment, and were required to provide written, informed consent to the study. Participants were not selected specifically for smoking behaviours, and therefore represent a broad cross-section of the typical cannabis and tobacco use patterns in the U.S.
Study subjects first underwent a baseline examination, followed by six follow-up examinations. Pulmonary (lung) function was tested at years 0, 2, 5, 10, and 20. By year 20, 69 percent of the original study participants remained in the study.
Lung function was tested by two metrics: Forced expiratory volume in the first second of expiration (FEV1) and forced vital capacity (FVC). The former measures the maximum volume of air that can be exhaled in one second, after fully inhaling. The latter measures the total volume of air that can be exhaled after full inhalation, and does not limit the measurement by time.
What Were The Results Of The Study?
For tobacco use, the results were as expected: both FEV1 and FVC steadily decreased with both current and lifetime exposure – yet more evidence that tobacco use causes long-term impairment to lung function.
But for cannabis use, the results were surprising: light exposure to cannabis (both current and lifetime) actually caused an increase in FVC, and light lifetime exposure also increased FEV1 measures. This means that, compared to individuals with zero exposure to cannabis smoke, total lung capacity in cannabis users increased over the twenty years of the study!
Furthermore, both FVC and FEV1 increased steadily when measured against “current marijuana smoking intensity” (defined as episodes of smoking in the preceding thirty days). Therefore, the more frequently the participants currently smoked, the higher their lung capacity was.
Heavier cannabis users did not fare quite so well in the long-term, as lifetime FEV1 gains levelled off or even reversed with increased exposure. However, even “very heavy marijuana use” was associated with lifetime FEV1 “not significantly different from baseline”, and FVC “remained significantly greater than baseline”.This suggests that even heavy cannabis smokers will not suffer a decline in total lung capacity over time (in fact, cannabis exposure may offer protective or augmentative effects), and that even if ability to forcibly exhale air in the first second is somewhat reduced, it is unlikely to be significant.
FEV1 is an important measure, and should normally be 70–80 percent of FVC; if it drops below 65 percent, it indicates narrowing of airways – a possible indicator of chronic obstructive pulmonary disease or COPD. Thus, even “heavy” cannabis use is not associated with an increased risk of COPD, although it may be advisable for individuals with other COPD risk factors to limit use.
On the other hand, the fact that light use increases lifetime FEV1 provides further evidence of its bronchodilatory effects, which in turn provides yet more evidence of its potential as a treatment for asthma, when used lightly and without tobacco.
This study was hailed as a landmark piece of research, as it went far beyond the time restrictions other similar studies are often limited to, and was able to establish long-term associations that can be held up as evidence of causation and not just correlation. Thus, with this study (along with several others like it that have focused on tobacco) we can safely say: tobacco use causes lung damage and disease, while cannabis use does not cause it.
Other Research On Cannabis, Tobacco & Lung Health
In 2015, the results of another important study were published, this time by researchers at Emory University in Atlanta, Georgia. The study assessed cannabis smoke exposure and lung health in a large representative sample of US adults, aged 18–59, and is the largest cross-sectional analysis to date examining associations between cannabis use and lung health.
Again, the study found that light cannabis use over a 20-year period (self-reported, in this case: as a cross-sectional analysis, this study did not actually track participants for 20 years) is not associated with adverse effects on lung health, and that it does not cause a decline in FEV1. Furthermore, the study authors noted that cannabis smoke exposure may confer a protective effect on the lungs, and that smokers of tobacco that also used cannabis may therefore be mitigating the deleterious effects of tobacco.
The study also noted that habitual cannabis users were more likely to report increased symptoms of bronchitis, despite not experiencing a concurrent decline in lung function, and that users who vaporised cannabis are likely to experience fewer or less severe symptoms of bronchitis.
As well as this, a 2013 review, Effects of Marijuana Smoking on the Lung (Tashkin, D.P.) concluded that exposure to cannabis smoke was not associated with the development of lung cancer, chronic obstructive pulmonary disease (COPD), emphysema, or bullous lung disease.
It concluded: “accumulated weight of evidence implies far lower risks for pulmonary complications of even regular heavy use of marijuana compared with the grave pulmonary consequences of tobacco”.
As we see here, there is now a substantial body of reliable research that provides very strong evidence for the relative safety of cannabis use in terms of lung health. Reassuringly, it seems that this weight of evidence is really changing minds about cannabis, and in a somewhat unexpected area – deep inside the mainstream corporate world of the insurance industry.
How Cannabis Research Has Helped Reshape The Insurance Industry
Recently, two Canadian insurance providers reversed their long-running policies on cannabis smokers, which previously classed them in the same category as tobacco smokers (and could lead to premiums three times higher than those aimed at non-smokers). Now, Sun Life and BMO Insurance will treat some cannabis users as non-smokers for life insurance policies.
Sun Life, the first company to announce the policy change, applies this change to all cannabis users that do not use tobacco, whereas BMO’s policy covers cannabis users that smoke up to two joints per week and do not use tobacco.
Sun Life stated while announcing the change: “In our industry, we keep up to date with medical studies and companies update their underwriting guidelines accordingly”, and that individuals would be assessed “at non-smoker rates, unless they also use tobacco.”
While the medical studies in question were not mentioned by name, the research we have discussed in the course of this article is likely to have been instrumental in these policy changes, and will no doubt guide other insurance companies towards similar changes in future.
Insurance For Cannabis Users In The U.S. & Europe
The situation in the U.S. is even more surprising. While medical cannabis users in the U.S. frequently experience problems and are charged higher premiums than non-smokers, a report from Bloomberg.com published in June 2015 stated that 29 percent of U.S. life insurers with official policies in place for cannabis users now class them as non-smokers.
Some insurers (such as New York Life Insurance Co.) implement policies based on frequency of use, whereby light to moderate use incurs no extra premium, but heavy recreational use incurs does incur an increased premium. While studies do suggest some long-term reduction in lung function in heavier users, this stance is still somewhat discriminatory, as no studies indicate a link to actual lung disease.
Thus, light-to-moderate cannabis users, especially those with proven medical need for cannabis, may find that finding life insurance is not so difficult in the U.S., provided one shops selectively. However, heavier recreational users may find it harder to obtain life insurance without paying increased premiums, despite a distinct paucity of evidence of any link to lung damage and disease.
We have clearly come vast distances in our efforts to legitimise cannabis, and these developments are hugely encouraging – but as ever, it’s clear we still have considerable work to do before the facts about cannabis are fully recognised.