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. Like slot machines, smartphones and apps are explicitly designed to trigger dopamine?s release, with the goal of making our devices difficult to put down.

This manipulation of our dopamine systems is why many experts believe that we are developing behavioral addictions to our phones. 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 ? like, say, you?re being charged by a bull. 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 email from your boss.

If they happened only occasionally, phone-induced 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, according to a tracking app called Moment. The result, as?Google has noted in a report, is that ?mobile devices loaded with social media, email and news apps? create ?a constant sense of obligation, generating unintended personal stress.?

?Your?cortisol levels are elevated?when your phone is in sight or nearby, or when you hear it or even?think?you hear it,? says David Greenfield, professor of clinical psychiatry at the University of Connecticut School of Medicine and founder of the Center for Internet and Technology Addiction. ?It?s a stress response, and it feels unpleasant, and the body?s natural response is to want to check the phone to make the stress go away.?

But while doing so might soothe you for a second, it probably will make things worse in the long run. 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 to make your anxiety go away. 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,? says Dr. Robert Lustig, emeritus professor in pediatric endocrinology at the University of California, San Francisco, and author of ?The Hacking of the American Mind.? ?And our phones are absolutely contributing to this.?

In addition to its potential long-term health consequences, smartphone-induced stress affects us in more immediately life-threatening ways.

Elevated cortisol levels impair the prefrontal cortex, an area of the brain critical for decision-making and rational thought. ?The prefrontal cortex is the brain?s Jiminy Cricket,? says Dr. Lustig. ?It keeps us from doing stupid things.?

Impairment of the prefrontal cortex decreases self-control. When coupled with a powerful desire to allay our anxiety, this can lead us to do things that may be stress-relieving in the moment but are potentially fatal, such as texting while driving.

By?Catherine Price for The New York Times

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