Alcoholics in recovery are more likely to relapse after three years if they smoke, according to a new study published in the journal Alcoholism: Clinical and Experimental Research.

Researchers from Columbia University’s Mailman School of Public Health and the City University of New York studied the results of 34,653 adults who participated in the National Epidemiologic Survey on Alcohol and Related Conditions. The participants were surveyed at two different points, three years apart, on their use of substances and other physical or mental disorders.

The researchers only reported on the data of those admitting to being chronic smokers and had a history of alcohol abuse. The smokers had double the chance of relapsing than the nonsmokers. Other factors did not interfere with these results.

The reason for these results are unclear, but they make it that much more important for those in recovery to quit smoking at the same time they quit drinking.