Study suggests frequency and severity of reactions to cannabis

The study notes that in the United States, medicinal cannabis use is now legal in 33 states, as well as the District of Columbia (D.C.). Meanwhile, 11 states, D.C., and Canada have legalized recreational cannabis use.

Consequently, more people who have not used cannabis before may try the drug in the future. As the authors note, these users “may have limited knowledge of the possible adverse effects of cannabis.”

The authors, therefore, wanted to find out more about what types of adverse reactions happen when someone uses cannabis, how likely they are to occur, and what factors might make a person more likely to experience them.

The team was specifically interested in acute adverse reactions, in which negative side effects happen for a short duration. The authors note that previous research has explored different chronic adverse reactions to cannabis use, whereas there is less research on acute adverse effects.

Dr. Carrie Cuttler, an assistant professor of psychology at Washington State University, Pullman, and one of the paper’s authors, notes, “There’s been surprisingly little research on the prevalence or frequency of various adverse reactions to cannabis and almost no research trying to predict who is more likely to experience these types of adverse reactions.”

“With the legalization of cannabis in Washington and 10 other states, we thought it would be important to document some of this information so that more novice users would have a better sense of what types of adverse reactions they may experience if they use cannabis.”

The researchers recruited 999 participants, all of whom were undergraduate students at the Washington State University’s Department of Psychology and had used cannabis.

72.7% of the participants were women, and 72.7% were white. Of the cohort, 94.8% used cannabis on a recreational, rather than medicinal, basis. Overall, 73.4% inhaled cannabis, and 11.4% used edibles.

Each participant filled in an online questionnaire that took approximately 30 minutes to complete. The questionnaire included 26 adverse reactions to cannabis, which the researchers compiled by reviewing past empirical research and speaking to cannabis users.

The participants had to answer yes or no to ever experiencing each of the adverse reactions. If they answered yes, they then rated how distressing the adverse reaction was on a five-point scale of 0–4, with 0 being not at all distressing and 4 being severely distressing.

The researchers also asked a subset of relevant participants (370 in total) how frequently they experienced acute adverse reactions when consuming cannabis — that is, what percentage of the times they consumed cannabis did they experience the adverse reaction.

The authors also determined whether the participants experienced signs of cannabis use disorder, which the National Institute on Drug Abuse define as the continued use of cannabis despite clinically significant impairment.

They also gauged:

• motives for using cannabis
• level of depression, anxiety, and stress
• anxiety sensitivity
• the Big 5 personality traits: neuroticism, extraversion, openness to experience, agreeableness, and conscientiousness.

More than half of the respondents reported the most prevalent acute adverse reactions to cannabis use; these were coughing fits, anxiety, and paranoia. The least prevalent were fainting, nonauditory or visual hallucinations, and cold sweats.

The adverse reactions that occurred most frequently were coughing fits, chest discomfort, and body humming (a buzzing or tingling sensation in the body). These reactions occurred 30–40% of the times the respondents used cannabis.

The reactions that the participants considered most distressing were panic attacks, vomiting, and fainting. They rated body humming, numbness, and feeling unsteady as the least distressing.

However, as Dr. Cuttler highlights: “It is worth noting even the most distressing reactions to cannabis were only rated between moderately and quite distressing. This suggests cannabis users do not, in general, find acute adverse reactions to cannabis to be severely distressing.”

The study found that people who were infrequent cannabis users were more likely to report acute adverse reactions.

Furthermore, people who used cannabis to fit in with others, showed signs of cannabis use disorder, or had anxiety sensitivity were more likely to report acute adverse reactions. These individuals were also more likely to experience distress to a significant degree.

“Interestingly, we didn’t find that quantity of use during a single session predicted very much in terms of whether or not a person was going to have a bad reaction,” says Dr. Cuttler. “It was the people who smoke on a less frequent basis who tend to have these bad experiences more often.”

The study did have some limitations. For instance, although its sample size was relatively large, the significant majority of the participants were white, female, recreational cannabis users.

This demographic skew may explain the discrepancies between the present study and previous research on acute adverse reactions to cannabis. The study authors give a 2007 study and a 2019 study as examples.

However, the study lays the groundwork for future studies, which will need to examine the adverse reactions to cannabis use in more detail, using a more diverse pool of participants.