There are so many harmful effects caused by smoking that it’s hard to decide where to start listing them. From health complications after surgery to brain damage, and even inflicting harm on our pets, the list can go on. Smoking is also believed to contribute to skin aging, and now a new study on twins shows that smoking can indeed cause premature wrinkling and other characteristics of accelerated aging.

Researchers scouted for twins at the annual Twin Days Festival, in Twinsburg, Ohio, to find pairs in which one twin smoked and the other didn’t, or both smoked, but with a five-year difference between initiation. They found 79 twins, of whom 57 were women, altogether with an average age of 48 years old. Close-up photos of each participants face were shown to a group of plastic surgeons, who had no knowledge of each participants’ smoking history. They were told to point out “specific components of facial aging” that were related to smoking, and 57 percent of the time, they were able to spot the smoking twin.

“Smoking makes you look old. That’s all there is to it,” Dr. Elizabeth Tanzi, a dermatologist at the Washington Institute of Dermatologic Laser Surgery, and who wasn’t involved in the study, told Reuters. Besides lung cancer, heart attacks, and strokes, just one more good reason to stop smoking is that it’s definitely making you look a lot older.”

The various indicators of aging that the surgeons found included: more sagging of the upper eyelids, baggier lower eyelids and bags under the eyes; more facial wrinkles, including lines between the nose and mouth, wrinkling of the upper and lower lips, and sagging chins. Signs of aging were most pronounced on the lower parts of the face, with those whose difference was more than five years showing even more signs, the researchers said.

Both twins smoked, however, the one on the right smoked for 14 years longer, as seen by more facial wrinkles. Plastic and Reconstructive Surgery/American Society of Plastic Surgeons.

“It is noteworthy that even among sets of twins where both are smokers, a difference in five years or more of smoking duration can cause visibly identifiable changes in facial aging,” they wrote.

The results held true even when environmental factors, such as work stress, alcohol consumption, and sunscreen use were accounted for. They also said that they could not control for the effect of smoking on fat distribution. A U.K. study found that “smokers on average have a lower body mass index than non-smokers.”

Study author Dr. Bahman Guyuron suggested facial creams and plastic surgery for people who have already damaged their skin from smoking, but told Reuters that the goal of the study was to encourage people never to start in the first place. “We are hoping that by again emphasizing the harms that come from smoking, we can dissuade individuals from smoking … knowing how much it may damage their skin,” he said.

Smoking kills more than five million people each year around the world, and is responsible for nearly 87 percent of lung cancer deaths, according to the National Institutes of Health. It also increases the risk for cancer by up to 23 times for men and 13 times for women, putting them at risk for cancer of the lips, oral cavity, esophagus, and many more.

Source: Guyuron B, Okado H, Alleyne B, et al. Facial Changes Caused by Smoking: A Comparison between Smoking and Nonsmoking Identical Twins. Plastic and Reconstructive Surgery. 2013.