New research conducted by Western Case Reserve University has found that persons with substance use disorders (SUDs) are at increased risk for COVID-19 infections, even after getting vaccinated (“breakthrough infections”). The highest rate of breakthrough infections occurred in individuals with cannabis use disorders.
In a population-based cohort study with 579,372 participants, the researchers assessed the risk, time trends, outcomes, and disparities of COVID-19 breakthrough infections in fully vaccinated SUD patients. They found that people addicted to substances such as alcohol, tobacco, cannabis, cocaine, or opioids had an almost double risk of contracting the coronavirus after getting both of their vaccine shots. Thus, while people without SUDs had a 3.6 percent rate of breakthrough infections, those with substance addictions had a seven percent rate.
In the case of cannabis use disorder, this rate increased to 7.8 percent. “Patients with cannabis use disorder, who were younger and had less comorbidities than the other SUD subtypes, had higher risk for breakthrough infection even after they were matched for adverse socioeconomic determinants of health and comorbid medical conditions with non-SUD patients,” the authors said.
However, as the scientists admit, additional variables, including behavioral factors or negative effects of cannabis use on pulmonary and immune functions could also contribute to the increased risk for breakthrough infections in this group.
Furthermore, cannabis advocates had already criticized this study, arguing that most cannabis users are not addicted and that there is no clear causal relation between cannabis use and increased risk of breakthrough infections.
“This study is limited to people with ‘substance use disorder’ which is a very small subset of cannabis consumers,” said Morgan Fox, the media relations director for the National Cannabis Industry Association.
“This is merely correlation and does not show a causal relationship … individual behavior patterns and social conditions may be a major contributing factor above and beyond simply exhibiting problematic substance use patterns, such as lack of access to reliable information, sharing joints, etc.”
“Clearly more study is welcome and necessary, but it is important not to overstate or misrepresent the very inconclusive results presented in this particular research and ensure that cannabis consumers are accurately informed about what the newest research actually indicates,” Fox concluded.
The study is published in the journal World Psychiatry.