Psoriasis and rheumatoid arthritis are chronic inflammatory disorders that can last for a long time. While both are often treated with methotrexate—a drug known for increasing liver disease risk—those with psoriasis who took this med faced a twofold risk for serious liver damage, according to new findings published in the Journal of Investigative Dermatology, reports Reuters.

For an average of six years, researchers at the University of Pennsylvania Perelman School of Medicine in Philadelphia reviewed information on nearly 1.3 million people without chronic inflammatory disorders in addition to 198,000 people with psoriasis, 12,000 with psoriatic arthritis and 54,000 with rheumatoid arthritis. (Those with inflammatory disorders who received systemic therapy, or medications that reached the whole body, were more commonly prescribed methotrexate.)

Findings revealed that people living with psoriasis were 37 percent more likely to develop liver disorders compared with those who didn’t suffer from chronic inflammatory diseases. What’s more, the risk of liver damage was doubled for people with psoriasis who took methotrexate.

Those with psoriatic arthritis, faced a 38 percent increased chance of liver disease without drug therapy; this increased risk rose to 67 percent with methotrexate. For patients with rheumatoid arthritis, there was no heightened risk of liver disease when on methotrexate. However, without drug therapy, their risk of liver damage increased by 49 percent. (The study didn’t track deaths as a result of liver disease or whether those at risk for the illness might have switched to other therapies.)

“Medications which are toxic to the liver, such as methotrexate, should be used cautiously in patients with psoriatic disease, especially those with additional risk factors, such as obesity or regular alcohol use,” said Joel Gelfand, MD, a professor of dermatology at the University of Pennsylvania Perelman School of Medicine in Philadelphia and the senior author of the study.

Researchers noted that apart from those common risk factors seen in liver disease, patients with psoriatic skin or joint disease—especially those with more acute skin psoriasis—showed an elevated risk for serious liver disease.

Another scientist who didn’t take part in the study cautioned that the harms and benefits of methotrexate, as well as nonsteroidal anti-inflammatory drugs, an alternative treatment for joint pain that also increases liver disease risk, should be carefully considered when treating those with inflammatory diseases.

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