Forcing employees to look happy in front of customers might have the opposite effect — it amplifies their negative emotions and makes them more likely to be heavy drinkers.

Employees forced to smile more are more likely to have a drink after work.

We all like the people who work for us to be friendly and smiley, but if you’ve worked in services with a lot of human contact, you probably know just how hard it can be to maintain a happy look. At some point, actually being happy isn’t an option, and you have to fake it — but this comes at a cost. A team of researchers at Penn State and the University at Buffalo found that resisting natural emotions and putting on a forced happy face makes people more likely to drink more alcohol.

By faking or suppressing emotions in front of customers, employees are using a lot of self-control. However, after work, there might not be all that much self-control left in the tank. So employees are left with very little self-control for their own emotions and for restricting their urges — urges such as drinking.

“Smiling as part of your job sounds like a really positive thing, but doing it all day can be draining,” Grandey said. “In these jobs, there’s also often money tied to showing positive emotions and holding back negative feelings. Money gives you a motivation to override your natural tendencies, but doing it all day can be wearing.”

Researchers analyzed data from 1,592 U.S. workers who routinely work with the public, such as people in food service who work with customers, nurses who work with patients or teachers who work with students. The data also included information about how often participants faked or suppressed emotions (something called “surface acting”) as well as how often and how much the participants drank after work. Overall, employees who interacted with the public drank more after work than those who did not. Furthermore, the more surface acting the employees had to use, the more drinks they tended to have. The association was stronger for employees who have a one-time relationship with the customer (such as a cafe or a bar) rather than for people who tended to develop a relationship with their clients (like a nurse or a teacher).

“The relationship between surface acting and drinking after work was stronger for people who are impulsive or who lack personal control over behavior at work,” Grandey said. “If you’re impulsive or constantly told how to do your job, it may be harder to rein in your emotions all day, and when you get home, you don’t have that self-control to stop after one drink.”

Of course, it pays to be nice to your customers. Another recent study, which was conducted by researchers at the University of Toronto and the University of South Carolina, found that particularly for small businesses, it’s essential to offer excellent customer support. Customers expect a warmer relationship with a smaller company as opposed to bigger businesses and tend to hold small businesses to a higher standard.

However, you shouldn’t push for over-the-top disingenuous fake smiles. Researchers call on businesses to re-think their “service with a smile” policies, and call for more natural interactions between employees and customers, especially in fields of work where the incentive to smile is commercial in nature.

“Nurses, for example, may amplify or fake their emotions for clear reasons,” Grandey said. “They’re trying to comfort a patient or build a strong relationship. But someone who is faking emotions for a customer they may never see again, that may not be as rewarding, and may ultimately be more draining or demanding.”