If you’re like many people, you may have decided that you want to spend less time staring at your phone.

It’s a good idea: An increasing body of evidence suggests that the time we spend on our smartphones is interfering with our sleep, self-esteem, relationships, memory, attention spans, creativity, productivity and problem-solving and decision-making skills.

But there is another reason for us to rethink our relationships with our devices. By chronically raising levels of cortisol, the body’s main stress hormone, our phones may be threatening our health and shortening our lives.

Until now, most discussions of phones’ biochemical effects have focused on dopamine, a brain chemical that helps us form habits — and addictions. Smartphones and apps are explicitly designed to trigger dopamine’s release, with the goal of making our devices difficult to put down.

But our phones’ effects on cortisol are potentially even more alarming. Cortisol is our primary fight-or-flight hormone. Its release triggers physiological changes, such as spikes in blood pressure, heart rate and blood sugar, that help us react to and survive acute physical threats.

These effects can be lifesaving if you are actually in physical danger. But our bodies also release cortisol in response to emotional stressors where an increased heart rate isn’t going to do much good, such as checking your phone to find an angry e-mail from your boss.

If they happened only occasionally, such cortisol spikes might not matter. But the average American spends four hours a day staring at their smartphone and keeps it within arm’s reach nearly all the time, said tracking app Moment.

“Your cortisol levels are elevated when your phone is in sight or nearby, or when you hear it or even think you hear it,” said David Greenfield, professor of clinical psychiatry and founder of the Center for Internet and Technology Addiction. “It’s a stress response. … the body’s natural response is to want to check the phone to make the stress go away.”

But any time you check your phone, you’re likely to find something else stressful waiting for you, leading to another spike in cortisol and another craving to check your phone. This cycle, when continuously reinforced, leads to chronically elevated cortisol levels.

And chronically elevated cortisol levels have been tied to an increased risk of serious health problems, including depression, obesity, metabolic syndrome, Type 2 diabetes, fertility issues, high blood pressure, heart attack, dementia and stroke.

“Every chronic disease we know of is exacerbated by stress,” said Dr. Robert Lustig. “And our phones are absolutely contributing to this.”