What Is a Cannabis User?

Apr 06, 2024

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Does cannabis cause schizophrenia, psychotic disorders, anxiety, depression or other mental illness?^[1] Heart attacks or strokes?^[2] Lung cancer?^[3] Some other health problem? There are tens of thousands of studies that try to determine the impact of using cannabis on various health and wellness outcomes. Most historic studies examine negative health outcomes associated with cannabis use, while more recent studies are recognizing health benefits from using cannabis.

But what is a cannabis user? How, exactly, is that defined?

When talking about the effects of cigarette smoking, one can differentiate between different intensities of use, such as:

(i) Casual or social smokers, who smoke perhaps a couple of cigarettes a month

(ii) Light smokers, who smoke maybe a few cigarettes a day

(iii) Heavy smokers, who smoke a pack or more a day.

When researchers and doctors talk about the effects of smoking cigarettes on health, the standard practice involves classifying smokers based on their smoking history, specifically the number of pack-years of use, that is, the number of packs per day the patient has smoked over a number of years. This classification system works because cigarettes are standardized, and the health effects associated with smoking a pack of cigarettes are relatively uniform across products and brands. And while no doctor would admit it’s healthy to smoke cigarettes, most doctors would presumably agree that casual smoking has very different health risks than heavy smoking.

Unlike cigarettes, however, cannabis products are not standardized. Cannabis products differ significantly in their respective profiles of active ingredients, as well as in their respective “serving sizes.” How do you compare use by one consumer who takes a puff of a joint or hit from a bong containing 15% THC from that by a consumer who smokes a gram joint of cannabis containing 30% THC from that by a consumer who eats a 10 mg THC gummy? And how do you account for differences in outcomes due to differences in consumers’ metabolisms and body systems, histories with cannabis, etc. (i.e., set and setting^[4])? And how do you distinguish people who have recently tried or started using cannabis with longtime users?

Surely, researchers will eventually classify cannabis users into groups akin to those used to classify cigarette smokers. However, historically, that has not been done. Rather, researchers simply lump anyone who has reportedly ever used cannabis into the category of “cannabis user.”

More recently, researchers have collected information to help distinguish light from heavy users, by asking whether or not they’ve consumed cannabis in the past year or the past month, and also by asking about their frequency of use in terms of number of days per week of use or number of uses per day. However, even these more recent studies still lump anyone who has indicated they have ever used cannabis into the cannabis user group. As a result, the nature of use by people classified as cannabis users is extremely heterogeneous, making it exceptionally difficult to draw any valid conclusions about the health effects of using cannabis. At the same time, another complicating factor is the fact that user-reported information about past cannabis use is unreliable, namely people under-report their use. But that’s a topic for another day.

The problems of

(i) standardizing cannabis use,

(ii) defining what it means to be a “cannabis user,” and

(iii) reliably characterizing differences between cannabis users and non-users

must be addressed. Unless or until what it means to be a cannabis user is more reliably defined and distinguished, studies on the health outcomes associated with “cannabis use” cannot be taken seriously.

Once that’s been done, then we can move onto the problem of determining health outcomes caused by using cannabis from those merely associated with using cannabis.

^[1] Is there a link between marijuana use and psychiatric disorders? NIH. 2023. https://nida.nih.gov/publications/research-reports/marijuana/there-link-between-marijuana-use-psychiatric-disorders

^[2] Jeffers, A. M., et al, Association of Cannabis Use With Cardiovascular Outcomes Among US Adults. JAHA. 2024. https://www.ahajournals.org/doi/10.1161/JAHA.123.030178

^[3] What are marijuana's effects on lung health? NIH. 2020. https://nida.nih.gov/publications/research-reports/marijuana/what-are-marijuanas-effects-lung-health

^[4] Hartogsohn, I., Constructing drug effects: A history of set and setting. Drug Science. 2017. https://journals.sagepub.com/doi/full/10.1177/2050324516683325

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