I am almost always stressed these days. Work is hectic. My ageing parents’ health is cause for concern. And to top it all off, my nine-year-old is nagging me to help him create an elaborate Halloween costume.

I would expect my cortisol levels to be sky high. But I’ve just completed the cortisol debt score assessment in Dr Erin Kinney’s new book The Cortisol Cure and they are apparently deficient. Over a Zoom call, I ask her to explain what’s going on.

The naturopathic doctor from Maryland in the US appears on my screen looking the picture of health, with shiny blonde hair, bright eyes, and a clear complexion. She says that, contrary to popular belief, cortisol is not the enemy.

“The hormone is produced in response to stress, but its function is to allow the body to generate the energy it needs to handle that stress,” she says. “It also plays a role in regulating circadian rhythms, peaking in the morning to wake us up and gradually declining throughout the day to prepare us for sleep. And it has an anti-inflammatory function. Cortisol has a bad reputation, but it’s vital to feeling well.”

When cortisol levels remain elevated over time, research suggests they may contribute to a range of health problems, including digestive issues, high blood pressure and heart disease. A 2022 Trinity College study also found that higher cortisol levels may help predict a person’s future risk of developing depression.

However, the body cannot sustain elevated cortisol levels indefinitely. In her book, Kinney argues that prolonged stress can eventually impair the body’s ability to regulate cortisol effectively, leading to a range of health problems.

Erin Kinney: ‘When we sleep, rest or relax, we earn cortisol and make a deposit.’Erin Kinney: ‘When we sleep, rest or relax, we earn cortisol and make a deposit.’

“These include exhaustion, migraines, weight gain, and low libido,” she says. “If you’ve been suffering from symptoms like these and standard tests haven’t found anything wrong, I’d recommend getting your cortisol checked. You need healthy reserves to function at your best.”

Kinney learned this lesson the hard way. In her 20s, she used to run marathons but didn’t pay enough attention to her diet, powering through on caffeine instead. Over time, she developed chronic fatigue, low mood and joint pain.

Medical tests proved inconclusive until a naturopath diagnosed low cortisol. “I expected my cortisol levels to be high because chronic stress has long been associated with elevated cortisol. But my naturopath told me that people don’t go to the doctor when cortisol is high because cortisol gives them energy to handle things. They only go when cortisol crashes and they can no longer cope. I had depleted cortisol and needed to rebuild it by focusing on rest and recovery.”

She did just that and found the experience so transformative that she decided to train as a naturopathic doctor.

Kinney compares cortisol to the currency used in the body’s bank account.

When we are physically, mentally or emotionally stressed, we spend cortisol and withdraw from the account. When we sleep, rest or relax, we earn cortisol and make a deposit.

Just as with our finances, we should earn and deposit as much as, or more than, we spend, she adds.

What Kinney did in her 20s and what she sees patients doing now is living in “go, go, go mode. They don’t sleep well. They don’t rest enough. Their cortisol account eventually runs out, and debt shows up as symptoms in the body.”

The more medical way of looking at cortisol is from the perspective of the nervous system.

Kinney explains that when the brain perceives a threat, it switches on the sympathetic nervous system, triggering the release of cortisol and adrenaline. These stress hormones speed up the heart rate and breathing to pump blood and oxygen to the muscles so that the body can either confront or flee from the threat. Once the threat passes, the parasympathetic system kicks in, restoring a state of calm.

“In sympathetic mode, you’re spending cortisol,” says Kinney. “In parasympathetic, you’re earning it back.”

A nervous system that is mostly in fight-or-flight mode causes a wide range of symptoms that can be attributed to a similarly wide range of health conditions. Kinney stresses that it’s important to rule these out before investigating cortisol.

She advises starting with “blood tests to check conditions such as thyroid dysfunction. If those come back clear and you’re still not feeling better, then get your cortisol checked”.

Her book outlines ways to support the body’s natural cortisol rhythm. And rest is central.

She understands that rest is difficult for many of us. “If the nervous system is used to being on alert, it will feel uncomfortable when you try to relax.”

The solution to this dilemma is to train our “rest muscle”. Kinney advises setting aside as little as five minutes a day for an activity we enjoy because “every time we do it, we teach our body it’s safe to relax”.

And for those who believe their lives are too busy to allow time for rest, she says:

“Stress leads to overwhelm and tasks taking longer to complete. By maintaining a relaxed state, you avoid overwhelm and in all likelihood get your work done faster”.

In her book, Kinney recommends simple practices such as lying down with our legs against the wall, getting morning light, meditation, taking a leisurely walk, and doing jigsaw puzzles.

“Reading fiction is surprisingly effective,” she adds. Research from the University of Sussex shows that just six minutes of reading can lower the heart rate and ease tension.

The one thing you shouldn’t do is scroll social media. According to Kinney, “the stories you encounter there can elicit stress and don’t give you the cortisol deposit you need”.

Whatever activity you choose, practice it daily. “And ignore any guilt you feel,” says Kinney. “The more you practice, the stronger your relax muscle gets and the more deposits you make to your cortisol account. Having reserves will give you the energy you need to better handle the inevitable stresses of life.”

To get a handle on my stress levels, I plan to put my feet up for 10 minutes after lunch today and have scheduled some reading time before bed. That’s if I don’t get waylaid by a nine-year-old wannabe zombie.

The Cortisol Cure: The Secret to Resetting Your Stress Response, Boosting Energy and Feeling Better Than Ever, Little, Brown Book Group, €20.12