Some electronic cigarette liquids contain enough alcohol to have an impact on motor skills, a new Yale University School of Medicine study shows.

E-cigarettes deliver nicotine by vaporizing liquids, which often contain alcohol and other chemicals. The new study, published in the journal Drug and Alcohol Dependence, found volunteers who used e-cigarettes with liquids with high concentrations of alcohol (23.5 percent) performed more poorly on tests of motor skills.

Some also had detectable levels of alcohol in their urine.

The researchers said the presence of alcohol might reinforce the addictive properties of both nicotine and alcohol if inhaled.

“Given the widespread and unregulated use of e-cigarettes, especially by youth and other vulnerable populations, further studies are needed to evaluate both the acute safety and long-term health risks of using alcohol-containing e-cigarettes,” said Mehmet Sofuoglu, of Yale’s Department of Psychiatry and VA Connecticut Healthcare system, who is senior author of the paper.