Smoking may not only cause wrinkles and sagging skin, it might also increase your risk of one type of skin cancer, researchers suggest in a new report.

Studies have linked smoking to a long list of health effects, including heart disease and lung cancer, but the evidence has been mixed for skin cancer.

More than 3.5 million cases of the disease are found every year in the U.S., making it the most common of all cancers. While the two main forms -- basal cell carcinoma and squamous cell carcinoma -- are rarely deadly, researchers say they are on the rise.

In a new study, Fiona Bath-Hextall of the University of Nottingham in England and colleagues pooled the available evidence on the link between tobacco and basal and squamous cell cancers, which start in the outer layer of the skin.

Based on 14 previous studies, smokers didn't appear to have higher rates of basal cell cancer. But they did have a 52-percent increase in their risk of squamous cell cancer, based on six studies that varied in size, duration and design.

That extra risk is similar to that of ultraviolet radiation, the most well-known risk factor for squamous cell cancer, according to a commentary published along with the new results in the Archives of Dermatology.

But the commentary, by Dr. Joris Verkouteren and Dr. Tamar Nijsten at Erasmus Medical Center in Rotterdam, the Netherlands, also warns that the six studies were relatively small and were not necessarily comparable.

Because all of the studies are based on observations, it's impossible to say for certain whether smoking caused the increase in skin cancer risk. While current smokers had a higher risk than former smokers, there was no link with the number of cigarettes smoked per day or how long a person had been smoking.