Smokers who take multivitamins appear to be lulled into a false sense that they are protecting their health, and end up smoking more than smokers who don’t take vitamins, according to a new study published in the journal Addiction.

As reported in the journal’s news release, many smokers who take vitamins incorrectly believe the pills will protect them against cancer. This belief deters them from cutting down on their smoking or quitting.

The study consisted of two parts, Medical News Today reports. In the first part, 74 daily smokers were given a placebo, or inactive pill. Half of the participants were told the pill was Vitamin C. All the participants then took a one-hour survey and were permitted to smoke. Those who thought they had taken a vitamin pill smoked almost twice as much as those who knew they took a placebo. Those taking pills they thought were vitamins also reported a greater feeling of invulnerability.

In the second part of the study, 80 participants were given a placebo; half were told it was a multivitamin. All the participants took a survey that included questions about their views on multivitamins. Smokers who thought they had taken a multivitamin smoked more than those who knew they were taking a placebo. Those who took what they thought was a multivitamin said they had more positive attitudes toward vitamins, and smoked more than those who were less positive about them.

The researchers wrote, “Reminding health-conscious smokers that multivitamins do not prevent cancer may help such smokers to control their smoking and encourage them to stop.”