Researchers say people keep buying bottled water, despite knowing the negative effect the plastic could have on the environment, because they are afraid of dying and are seeking immortality.

The idea comes from a study into the messages of bottled water advertising, both overt and covert, as well as those of public anti-bottled water campaigns.

“We found that pro-bottled water advertisements had a greater capacity to manage death anxieties because they better support the audiences’ self-esteem, provide the audience with opportunities to engage in worldview defense, and symbolically extend the consumers’ perceived lifespan,” according to a study in the journal Applied Environmental Education & Communication.

The messages of the bottled water advertisements play into people’s worry about dying in part through the fear of tainted water.

“Our mortality fears make us want to avoid risks and, for many people, bottled water seems safer somehow, purer or controlled,” researcher Stephanie Cote said in a statement from the University of Waterloo. “There is also a deeper subconscious force at work here, one that caters to our desire for immortality.”

The research was connected to the Terror Management Theory, a concept in psychology that suggests certain behaviors can be attributed to people unconsciously trying to mitigate their fear of dying. Those behaviors can include how people spend their money and what they buy.

“Our results demonstrate that corporate campaigns appeal to people who measure their personal value by their physical appearance, fitness levels, material and financial wealth, class and status,” researcher Sarah Wolfe said in the Waterloo statement. “Pro-bottle water advertisements rely heavily on branding, celebrity and feel-good emotions that trigger our group identities and patriotism.”

The research took place in Canada but the U.S. has a bottled water fixation as well — Americans spend billions of dollars every year on it.

According to the study, the findings hold lessons on strategy for officials who are trying to get more people to cut down on bottled water.

“Environmental campaigns provide information to encourage people to alter their behaviors but with mixed success,” the study explains. “Terror Management Theory — and the influence of mortality reminders — offers a useful framework for understanding environmentally significant behaviors, and provides critical insights for developing more effective environmental communications.”