A study offers yet another good reason not to smoke: There is a link between smoking and psoriasis. Smoking increases your risk of developing the skin condition, and the more you smoke, the greater your risk.

The study, published by U.S. and Canadian researchers in The American Journal of Medicine, is the largest prospective study of smoking to date. Using data from the Nurses Health Study II – an ongoing study of 116,608 female registered nurses from 15 states between the ages of 25 and 42 years who completed and returned an initial questionnaire in 1989 – the researchers documented 887 incident cases of psoriasis during the 14 years of follow-up. Lifetime smoking exposure was measured in pack-years, equal to smoking 20 cigarettes per day for one year.

Compared with women who never smoked, the risk of psoriasis was 37 percent higher among past smokers and 78 percent higher among current smokers. The link between psoriasis and smoking became more apparent as the number of pack-years increased.

The good news: The risk of psoriasis decreased slowly when smokers stopped smoking. Psoriasis risk after 20 years of not smoking, the researchers found, was no greater than for those who had never smoked.