If you’re a smoker, here’s another reason to quit: a large study suggests that smokers have an increased risk of developing the chronic skin condition psoriasis.

Experts believe the disease, which causes thick, red, scaly patches on the skin, is triggered by an abnormal immune system attack on the body’s own cells, and since smoking can affect immune activity, some studies have suggested smokers are more vulnerable to it.

In a new study, researchers analyzed data from three large, long-running studies of U.S. health professionals. Of the nearly 186,000 people followed for 12 to 20 years, researchers found current smokers were almost twice as likely as lifelong non-smokers to develop psoriasis. In addition, past smokers had a 39 percent higher risk than non-smokers.

While these findings, reported in the American Journal of Epidemiology, do not prove that smoking causes psoriasis in some people, senior researcher Dr. Abrar A. Qureshi, of Harvard Medical School and Brigham and Women’s Hospital in Boston said it’s clear that in the study subjects, the smoking came before the psoriasis.

“I think if there’s one message, it’s that for now, smoking seems to be a risk factor for new-onset psoriasis,” Qureshi told Reuters Health.

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