Over the course of the smartphone revolution, much research has been conducted on how our phones affect our health and their negative impact on everything from our eyes to our brains. Many of those studies have focused on smartphones’ relationship with dopamine, the chemical released in our brains which is instrumental in forming habits and addictions. Science has found many phones and apps are specifically designed to trigger the release of dopamine to get us as addicted to checking and interacting with our devices.

Research has shown the average American “spends four hours a day staring at their smartphone and keeps it within arm’s reach nearly all the time”. That is probably the same for people in other countries.

According to a recent report in the New York Times, there’s another chemical smartphones affect which we should be worried about and which poses risks to our long-term health - and maybe even survival. Cortisol is the body’s primary hormone for dealing with stress. It is released in situations where our fight-or-flight response kicks in, intended to help us deal with highly stressful or life-threatening situations. It’s disturbing to think that seeing an anxiety-inducing email late at night might have the same physical effect as the sight of an angry bear charging towards you but that’s what new studies suggest might be happening.

As Google observed in a report, “mobile devices loaded with social media, email and news apps… [create]…a constant sense of obligation, generating unintended personal stress”.

The NYT quotes professor of clinical psychology at the University of Connecticut David Greenfield as warning that “cortisol levels are elevated when your phone is in sight or nearby or when you hear or even think about it”.

“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.”

The repetition of this cycle of anxiety leads to abnormal spikes in cortisol levels, which carry serious health risks. Elevated levels of the hormone have been linked to “a series of health problems, including depression, obesity, metabolic syndrome, type 2 diabetes, fertility issues, heart attack, dementia and stroke”.

As Dr Robert Lustig, emeritus professor in pediatric endocrinology at the University of California, San Francisco, told the paper, high levels of cortisol impair the prefrontal cortex – the area of the brain responsible for decision making and rational thought – what he describes as “the Jiminy Cricket” of the brain, which “keeps us from doing stupid things”.

If our Jiminy Cricket isn’t working it affects our self-control and can lead us to do things that might be momentarily relieving but are also potentially stupid and destructive – like reaching for our phones to respond to text messages while driving or not looking where we’re going while walking because we’re so obsessed with replying right this second.

So what to do about these potentially life-threatening, stress-inducing smartphone side effects? If you work towards curbing some of your bad phone habits it can help your brain and body keep hormone levels normal.

You can start by turning off unnecessary notifications. Also take note of the way apps make you feel. If Twitter makes you angry, don’t go on it. You can also take long, initially twitch-inducing but ultimately beneficial, breaks from your phone. You don’t have to go all-out and start with a 24-hour no-tech-use cleanse. Start slowly by doing things like not taking your phone with you during your lunch break or switching it off during dinner.

It is getting harder and harder to introduce self-protective timeouts but it’s up to us to make the effort before manufacturers are forced to put health warnings on phones and hide behind that tobacco firm defence - “we told you so, so not our problem”.