Daily use of cannabis is strongly associated with chronic inflammation, study finds

Recent research has found that individuals who use cannabis daily or nearly daily tend to have elevated levels of soluble urokinase plasminogen activator receptor (suPAR), a marker of chronic inflammation. In contrast, less frequent cannabis use was not associated with increased levels of this inflammation indicator. The research was published in Psychological Medicine.

Cannabis is a plant genus that includes species such as Cannabis sativa, Cannabis indica, and Cannabis ruderalis. It is widely known for its psychoactive properties, primarily due to compounds called cannabinoids—especially tetrahydrocannabinol (THC). Another major cannabinoid, cannabidiol (CBD), is non-psychoactive and is often used for therapeutic purposes.

Cannabis can be consumed in a variety of forms, including smoking, vaporizing, edibles, and oils. It has a long history of both recreational and medicinal use, with applications in pain relief, anxiety, nausea, and epilepsy. Legal status varies around the world, with some countries fully legalizing it, others permitting only medical use, and many maintaining strict prohibitions.

Long-term or heavy cannabis use has been linked to cognitive impairment, dependence, and mental health issues. More recently, researchers have proposed that frequent cannabis use may contribute to chronic inflammation in the body. This inflammation could in turn play a role in the development of psychosis and other serious mental illnesses associated with cannabis use.

Study author Emmet Power and his colleagues sought to investigate whether cannabis use—particularly daily or near-daily use—is associated with immune system activity and inflammation.

To do this, the researchers examined levels of four biomarkers: interleukin-6 (IL-6), tumor necrosis factor-alpha (TNFα), C-reactive protein (CRP), and soluble urokinase plasminogen activator receptor (suPAR). These markers are involved in immune and inflammatory responses, and elevated levels can indicate infection, chronic inflammation, or increased risk for conditions such as cardiovascular disease, cancer, or sepsis.

The researchers used data from the Avon Longitudinal Study of Parents and Children (ALSPAC), a long-term cohort study that enrolled 14,541 pregnant women living in a specific region of southwest England with expected delivery dates between April 1, 1991, and December 31, 1992. The study initially gathered health-related data from the parents and later continued collecting data from the children themselves.

When the children reached age 24, 3,257 of them were still participating. For the current analysis, the researchers used data from 914 participants in this group. Among them, 22% met criteria for major depressive disorder, 29% for anxiety, and 10% had experienced psychotic symptoms in the previous six months.

Participants provided blood samples, allowing researchers to assess biomarker levels. They also answered a single question about how often they used cannabis and provided additional health and demographic information.

The results showed that just under 5% of participants used cannabis daily, 7% used it weekly or monthly, and 21% reported using it less than once a month. Cannabis use was not associated with IL-6, CRP, or TNFα levels.

However, daily or near-daily cannabis use was strongly associated with elevated suPAR levels. In other words, people who used cannabis frequently tended to have higher levels of this particular marker of inflammation. Less frequent cannabis use did not show this association.

“In summary, our study found that daily/near daily cannabis use is strongly associated with elevated levels of suPAR, a marker of chronic inflammation, at age 24. The relationship between cannabis use and elevated suPAR in particular raise intriguing questions about mechanisms that may underpin the relationship between cannabis exposure; psychotic disorder; and potential roles of frequent cannabis use in oxidative stress, and potential role in chronic diseases in multiple systems,” the study authors concluded.

The study sheds light on the links between cannabis use and immune system activity. However, it should be noted that the design of this study does not allow any causal inferences to be derived from the results.

The paper, “Cannabis use in youth is associated with chronic inflammation,” was authored by Emmet Power, David Mongan, Colm Healy, Subash Raj Susai, Melanie Föcking, Stanley Zammit, Mary Cannon, and David Cotter.