Marijuana Use Linked to Higher Rate of ‘Breakthrough’ COVID-19 Cases

Nancy Grover

Sarasota, FL ( – Employers trying to determine best practices to protect their workers from the coronavirus have a new aspect in the mix. Research suggests people with substance use disorders (SUD) may have a higher likelihood of infection than others – even after they have been fully vaccinated.

A study published in the journal World Psychiatry indicates among those with SUDs, use of cannabis was especially associated with ‘breakthrough’ COVID0-19 cases, that is, contracting the virus after being fully vaccinated. But marijuana advocates caution against reading too much into the study, saying the findings are inconclusive and should not be misrepresented.

The Research

Researchers from the U.S. National Institutes of Health and Case Western Reserve University conducted a population-based cohort study of people who had been fully vaccinated between December 2020 and August 2021. Among the 579,372 individuals included were 30,183 with a diagnosis of SUD.

The Substance Abuse and Mental Health Services Association says SUDs occur “when the recurrent use of alcohol and/or drugs causes clinically significant impairment, including health problems, disability and failure to meet major responsibilities at work, school or home.”

A number of comorbidities prevalent among those with SUDs are risk factors for severe outcomes of COVID-19, including cardiovascular, cerebrovascular, immune, hematological, pulmonary, metabolic, oncological, hepatic, renal, infectious, neurological and psychiatric diseases, according to the researchers. “Additionally, studies from the early pandemic showed that patients with SUDs – including alcohol use disorder, cannabis use disorder, cocaine use disorder, opioid use disorder, and tobacco use disorder – were at increased risk for COVID-19 infection and associated severe outcomes, especially among African Americans.”

The authors estimated the risk for breakthrough infection rates among vaccinated persons with SUDs against those with no SUDs. They assessed the risk, time trends, outcomes and disparities of breakthrough infections beginning 14 days after completion of vaccination.

“Vaccines are very effective,” the researchers wrote, “but breakthrough infections have been recorded, highlighting the need to identify populations that might be most vulnerable, as we have entered a worrisome new phase of the pandemic.”


The risk for breakthrough infections among SUD patients was significantly higher than the 3.6 percent in the non-SUD population, according to the researchers. It ranged from 6.8 percent for tobacco use disorder to a high of 7.8 percent for cannabis use disorder patients. However, those numbers were not statistically significant when adjustments were made – for most SUD categories.

“When we matched SUD and non-SUD individuals for lifetime comorbidities and adverse socioeconomic determinants of health, the risk for breakthrough infection no longer differed between these populations, except for patients with cannabis use disorder, who remained at increased risk,” the researchers wrote. “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. This may indicate that additional variables, such as behavioral factors or adverse effects of cannabis on pulmonary and immune function, could contribute to the higher risk for breakthrough infection in this group.”

Marijuana Advocates

Cannabis users with the clinical diagnosis of SUD represent “a very small and distinct subset of the cannabis consuming community,” said Paul Armentano, deputy director of the National Organization for the Reform of Marijuana Laws, “and it is possible that they may possess certain behavioral traits or characteristics that place them at higher risk.”

Armentano said the study raises more questions than it answered. He also said the vast majority of cannabis consumers without a SUD diagnosis were likely included in the control group. “Therefore, we have no idea from these findings what elevated risks, if any, these non-classified consumers – who comprise the overwhelming majority of marijuana users – possess.”

Advocates also pointed to the study’s limitations and nuances stated by the authors; “that this is merely correlation and does not show a causal relationship; and that 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 or sharing joints, etc,” said Morgan Fox, Media Relations Director/Committee Manager for the National Cannabis Industry Association. “Since this study is limited to individuals with problematic cannabis consumption patterns, the main message should be to use cannabis responsibly, and to make sure that you are taking all necessary precautions to not engage in behaviors that put you at greater risk of pathogen transmission, regardless of whether those behaviors are related to your cannabis consumption.”

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