By Vivienne Parry
Presenter, BBC Radio 4's Stressed Out
"I could feel my blood boiling, my pulse is racing, my heart's going.
Stress can damage physical health
"My muscles get more and more tense, my heart's getting faster and faster, there's a pain in my chest - I'm a gibbering wreck'.
"When it comes to bedtime I'm tired and try to make myself go to sleep, but I can't, my mind is racing and my thoughts whirling."
These are the words of John and Anne and what they are describing are the all too familiar symptoms of stress.
Stress is a constant theme in our lives.
It is the second biggest cause of time off work and is estimated to cost the country £13bn a year.
We clearly are not coping well with it, but how sick is it making us?
We all differ in what hits our own particular stress buttons - deadlines at work, being late, traffic jams - or what does it for me, computer rage.
This differing response makes stress difficult to research.
But researchers at a unique stress research facility in the Integrative Neuroscience and Endocrinology at the University of Bristol have found a way.
An individual's blood pressure and heartbeat are recorded before and after they breathe an air mix containing 35% carbon dioxide for four seconds.
Normal air contains just 0.03% of this gas. This prompts an acute - and automatic - physiological stress response.
And it's what I found myself doing for the programme.
At the start, my heartbeat was 54 per minute and my blood pressure a healthy 110/65.
I knew I was safe, but my body disagreed violently - it thought I was being suffocated.
My blood pressure shot through the roof - to 193/65. I felt sick and panic stricken. It was horrible.
But a couple of minutes afterwards, I was back to normal again.
The initial but dramatic rise is normal. In those who are chronically stressed, the return to normality is much slower.
"Their body is able to turn their acute stress response on, but is not as good at switching it off again," said Professor Stafford Lightman, director of the Bristol unit.
As Professor Simon Wessely, of King's College Hospital says, an acute stress response is actually good news: "It allows you to react to an emergency."
A bear jumping out at you in the street will prompt a flood of the stress hormones, first adrenaline and then cortisol, preparing you for fight, flight or fright.
Robert Sapolsky, professor of Biological Sciences at Stanford University and the world's leading stress researcher, summarised it like this.
"Your body is turning off all the long term building and repair projects. It's do it tonight, if there is a tonight'.
"So blood pressure soars, more body fuel in the form of glucose is made available, the immune system is enhanced.
"It's a wonderful adaptation should you come across a bear. But too much of a good thing and you're in trouble."
Constant high levels of cortisol take your body's eye off the ball.
Repairs aren't done, patrols for invaders aren't sent out, you tire more easily, you can become depressed and reproduction gets downgraded.
High bloodstream levels of glucose and fatty acids and high blood pressure increase the risk of cardiovascular disease and diabetes. The immune system is suppressed.
Work at Bristol clearly demonstrates the latter in the much reduced response of older carers of those with Alzheimers to flu vaccines, compared to people of the same age not under so much stress. But why are some people more affected by stress than others?
Professor Stafford Lightman, director of the Bristol Centre, said: "There are three main reasons.
"Our genes, our experiences in early life and what's happened to us recently."
We all understand the latter. Bereavement, losing a job, divorce, caring for someone who is sick are highly stressful life events.
Of great scientific interest are our stress 'thermostats' which switch our response on, and, most importantly, off again.
Professor Lightman said: "Understanding pathways in dysfunctional stress responses means that you can rationally design therapies to block their effect."
The settings for our thermostats are partly inherited - but scientists also know that they can be reset during childhood.
Work with animals suggests that emotional deprivation in early life causes heightened stress responses as adult animals. It's highly likely this is the case for people too.
Re-setting the stress thermostat in childhood is an important adaptation - it equips a child born into a difficult world to be constantly on the alert.
But this alertness comes with a long term price: heart disease, diabetes, obesity and depression.
There are also behavioural implications of raised stress hormones, such as greater levels of violence and risk taking.
Since we now have epidemic levels of cardiovascular disease and diabetes, does this indicate that we live in a much more stressful world? The answer is a resounding no. If anything we live much less stressful lives than our forbears.
Professor Sapolsky said: "It's a profound privilege to die from stress related diseases.
"It is the elimination of other causes of death such as infectious disease which is responsible for bringing lifestyle diseases to the fore - and these are exquisitely sensitive to stress."
It makes finding a way to treat stress in those who are vulnerable to it ever more important.
Stressed Out will be broadcast on Radio 4 at 2100BST on Wednesday 7 September. You can also listen online for 7 days after that at Radio 4's Listen again page.