Having an occasional cigarette may affect drinking habits more than you think.

A new study from Yale University School of Medicine and the University of Pittsburgh finds non-daily or “casual” smoking is linked to an increased risk of hazardous drinking and alcohol-use disorders (AUDs). Non-daily smokers are a fast-growing group that make up at least 25-percent of all adult smokers in the United States.

Researchers surveyed 5,838 adults aged 18 to 25 on things like how much they smoked during the preceding 12 months, how much they drank a week, and how frequently they went binge drinking.

The report shows casual smokers were 16 times more likely than non-smokers to be hazardous drinkers and five times more likely to meet the criteria for an AUD.

“We anticipated that the associations between alcohol use and smoking would be greatest in non-daily smokers, but were surprised by the degree of the associations,” Sherry A. McKee, researcher at Yale University School of Medicine, was quoted as saying. “While casual smoking was more usual in college students, the relationships between smoking and drinking behavior were the same for young adults whether they were students or not.”

“Even though daily smokers drank more, non-daily smokers drank more hazardously,” Saul Shiffman, researcher at the University of Pittsburgh, was quoted as saying. “This, in conjunction with other research,] suggests that these casual smokers neither smoke nor drink regularly, but rather may have periodic binges where they may do both, perhaps as they become disinhibited at parties. Drinking and smoking may also mutually promote each other, leading to bouts of heavy drinking and smoking.”

The researchers say the strong links between smoking and drinking suggest understanding the association could teach us a lot about both behaviors.

SOURCE: Alcoholism: Clinical & Experimental Research, published online September 23, 2008

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