A new study by researchers at the University of California San Diego School of Medicine has found that daily use of e-cigarettes alters the inflammatory state of the brain, heart, lungs, and colon, according to Medical Xpress.

The study, which appeared Tuesday in the journal eLife, also found that effects vary depending on the e-cigarette flavor and can influence how organs respond to viral infections, including COVID-19.

This is the first study to assess JUUL devices and their flavors in a multi-organ fashion.

The study’s senior author Dr. Laura Crotty Alexander, “These pod-based e-cigarettes have only become popular in the last five or so years, so we don’t know much about their long-term effects on health.”

In the United States, more than 12 million adults use e-cigarettes, with the highest rates of use among people aged 18 to 24.

Dr. Crotty Alexander and her team focused on the current most prominent e-cigarette brand, JUUL, and its popular flavors such as mint and mango.

In the study, young adult mice were exposed to flavored JUUL aerosols thrice a day for three months. The researchers looked for any signs of inflammation across the body.

The team saw the most striking effects in the brain, where several inflammatory markers were elevated. Additional changes in neuroinflammatory gene expression were noted in the nucleus accumbens, a brain region critical for motivation and reward-processing, according to Medical Xpress.

The researchers said the findings raise major concerns, as neuroinflammation in this region has been linked to anxiety, depression, and addictive behaviors, potentially exacerbating substance use and addiction.

Dr. Crotty Alexander said, “Many JUUL users are adolescents or young adults whose brains are still developing, so it’s pretty terrifying to learn what may be happening in their brains considering how this could affect their mental health and behavior down the line.”

The team also found that there was an increased inflammatory gene expression in the colon. However, the heart showed decreased levels of inflammatory markers. The authors explained that this state of immunosuppression could make cardiac tissue vulnerable to infections.

In addition, there were numerous gene expression changes in the lungs, calling for further study of the long-term effects of pod-based e-cigarettes on pulmonary health.

The researchers also found that the inflammatory response of organs varied depending on which JUUL flavor was used. For instance, the hearts of mice that inhaled mint aerosols were much more sensitive to the effects of bacterial pneumonia compared to those that inhaled mango aerosols, per Medical Xpress.

Dr. Crotty Alexander said, “This was a real surprise to us. This shows us that the flavor chemicals themselves are also causing pathological changes. If someone who frequently uses menthol-flavored JUUL e-cigarettes was infected with COVID-19, it’s possible their body would respond differently to the infection.”

“It’s clear that every e-cigarette device and flavor has to be studied to determine how it affects health across the body,” said Crotty Alexander.