A ground-breaking 20-year study investigated the links between tobacco, cannabis, and lung function. It found that while tobacco caused adverse effects, cannabis did not. As a result of this study and others like it, healthcare providers are beginning to pay attention, and some health insurers are even starting to cover medicinal cannabis costs!
In 2012, a ground-breaking 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 get a full picture of potential associations. Many other studies that simply look at a brief window in time are 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. It 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 take an in-depth look at the findings of the study and other related studies that have since been published, and discuss the practical changes these findings have brought about within the industry.
What did the cannabis vs tobacco 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 clearly defined link. Therefore, this study aimed to resolve the issue once and for all.
Medicinal cannabis is of continuously growing importance in healthcare throughout the world; the number of users is increasing every year, as is the legitimacy of cannabis as a treatment for multiple afflictions. 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 5,115 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. CARDIA aims to study variables such as race, height, waist circumference, smoking habits, and second-hand 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. They were not selected specifically for smoking behaviours, and were therefore representative of a broad cross-section of the typical cannabis and tobacco use patterns in the U.S. The participants were aged 18 – 30 years and healthy at time of enrolment. All were required to provide informed written consent to the study.
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.
Their 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. This is yet more evidence that tobacco use causes long-term impairment to lung function.
For cannabis use, the results were surprising: light exposure to cannabis (both current and lifetime) caused an increase in FVC. 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 actually 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 a lifetime FEV1 ‘not significantly different from baseline’, and FVC ‘remained significantly greater than baseline’.
What do the results mean for cannabis users?
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. Additionally, even if the 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% of FVC. If it drops below 65%, this indicates narrowing of the airways – a possible indicator of chronic obstructive pulmonary disease (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’ cannabis use increases lifetime FEV1 provides further evidence of its bronchodilatory effects. In turn, these results underline the potential of cannabis as a treatment for asthma, when used lightly and without tobacco. Naturally, vaporising is a far better option for asthma sufferers who wish to use cannabis.
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 are proven evidence of causation, 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 and lung health
The above study is by far the most in-depth, providing insight into long-term cannabis use and tobacco use side by side. But it’s definitely not the only one. Here are some other studies that appear to support the same conclusions.
Emory University 20-year study finds cannabis use may even offset harmful tobacco use
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) isn’t associated with adverse effects on lung health, and that it doesn’t cause a decline in FEV1.
Furthermore, the study authors noted that exposure to cannabis smoke may confer a protective effect on the lungs, and that tobacco smokers who also used cannabis may therefore be mitigating the harmful 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.
2013 review finds cannabis is not linked to lung cancer and other ailments associated with tobacco use
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’.
2016 study confirms cannabis is not linked to ischemic stroke
A very large study published in the American Heart Association journals in 2016 attempted to identify any association between cannabis use and early onset stroke. Participants included nearly 50,000 Swedish men. This study found that unlike tobacco use, cannabis did not appear to be linked to early onset stroke. While heavy cannabis use was linked to ischemic stroke, the actual risk diminishes when accounting for simultaneous tobacco use.
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. One study even determined cannabis use to be over 100 times less deadly than alcohol use.
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, has applied this change to all cannabis users that don’t use tobacco. BMO’s policy covers cannabis users that smoke up to two joints per week and don’t 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’.
It isn’t just life insurance companies which are starting to accept the use of cannabis, either. More and more health insurance companies are covering the cost of ‘medical marijuana’. In New York, government-backed insurance may even be required to cover it soon. Lawmakers believe it’s unfair to not cover it, seeing how thousands of people use it and how it can be even more effective (and safer) than opioids currently used.
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. and Europe
The situation in the U.S. is even more surprising. Medicinal cannabis users in the U.S. frequently experience problems and are charged higher premiums than non-smokers. But a report from Bloomberg.com published in June 2015 stated that 29% of U.S. life insurers with official policies in place for cannabis users now classify 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 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 medicinal need for cannabis, may find that obtaining 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 while these developments are hugely encouraging, it’s clear we still have considerable work to do before the facts about cannabis are fully recognised.
- Disclaimer:This article is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with your doctor or other licensed medical professional. Do not delay seeking medical advice or disregard medical advice due to something you have read on this website.