Contrary to what you might think, anxiety is a normal experience. It's a protective mechanism which everyone has - and if we didn't have it, then we wouldn't function too well.
But the boundary between beneficial anxiety and the kind which becomes a hindrance is becoming blurry. So how do you know if you need to seek help, or if you just have a case of pre-exam or interview jitters?
"A clear indication of an anxiety disorder is if you find it difficult to concentrate or settle, and if, when you start addressing a certain worry, another pops up and you end up worrying about something else," explains Dr Paul McLaren, a consultant psychiatrist at The Priory Hospital, Hayes Grove.
The anxiety response can go wrong in "a number of ways", according to McLaren.
One of these ways is a panic attack which is essentially "sheer terror".
"The anxiety system gets switched on to max. It’s as if our life is in imminent danger even though there is no threat there, no one coming at us with a spear, no tiger ready to pounce.
"We have a strong urge to run, or we get paralysed and stuck to the spot. When the anxiety system gets switched on like this, although it is a false alarm, the brain scans for an explanation and usually finds one in our physical state."
While someone is in the throes of a panic attack, their blood pressure goes up, their heart thumps inside our chest, they shake, sweat, over-breathe and the brain interprets those changes as signs of imminent catastrophe.
"Common thoughts that pop up are ‘I’m having a stroke', 'I’m having a heart attack' or 'I’m going mad'", McLaren continues. "It is common for people experiencing panic for the first time to end up in the emergency room. It comes on, it peaks and then goes off, like a wave breaking. It leaves them drained and exhausted."
Once someone has a panic attack in a particular situation such as a supermarket, or train or even the office, the brain makes a connection between that place and the anxiety response.
"That leads to a build up of anxiety when you try to go back there or even think about it. In some people panic attacks recur and lead to panic disorder. n this, avoidance is often the main problem. People can stop going to work, or shopping, or on the train, or in extreme cases agoraphobia, when we try to avoid going away from the place we feel safe, usually home."
Liam Sheasby was in his final year of a BA journalism course when he developed an anxiety disorder following a severe bout of gastritis.
"My stubbornness to finish university rather than take a year off to recover meant I was constantly in a nervous state and petrified my stomach would make noises, or I'd suddenly need to rush to the toilet," Liam says.
"I was embarrassed, ashamed, miserable and this made me anxious about going to class and going out. Would I be in range of a toilet, would I be able to do the things I used to do, would I enjoy myself?"
Ultimately, he says, the answer was no.
"I became reclusive. I still went to classes but this was as much of the anxiety as I could handle. I’m a keen gamer so I took up World of Warcraft to provide distraction and an element of social interaction while I continued my studies and this did help a lot."
Liam graduated in June 2010 with a 2:2, missing out on a 2:1 by just 10 marks, which he attributes to being ill and not opting to retake the year.
The 25-year-old's anxiety developed, and turned into a "vicious cycle of worrying about nothing, thus caushing the problem I was worrying about".
"The anxiety developed into not just stomach-related (and in actual fact that’s a lot better for me now) but panicking if I got hungry because I’d come to associate stomach rumbling as illness, which would trigger adrenaline and that in turn affected my bowels.
"I’d made plans to visit friends and go on weekend trips and stuff, and my anxiety flared up at all of these events and so I began to dread travelling too."
Time and experience helped Liam, he says, and slowly working at fixing various issues such as the hunger panic and the fear of travelling.
"It took months if not years of effort but I got there. I’m just glad I’ve made a success of things now and I’m optimistic for life.
Now I work for the Press Association. I moved to Bristol, I haven’t had more than five minutes of anxiety in five months, and I’m generally alright bar remnants of the IBS.
"Things got better. I was one of the lucky ones."
The other main way the anxiety system can malfunction is generalised anxiety disorder (GAD), which, in contrast to panic attacks, is a more constant background level of anxiety.
"The two main symptom groups are worries and physical symptoms associated with the anxiety response," McLaren says. "The physical symptoms can be caused by increased muscle tension, irritation of the bowel, an increase in heart rate. Muscle tension can cause headache and chest pain which the brain in the anxious state can then interpret as serious physical problems.
"The worry symptoms can be about our health or the health of loved ones, but when the anxiety response is switched on in GAD the brain will find a focus for the fear.
"Unless the anxiety is switched off then as soon as one worry is resolved the brain latches on to another and another. It is often the physical symptoms which bring sufferers of GAD for treatment."
Other ways in which the anxiety system can malfunction include obsessive compulsive disorder (OCD) and post-traumatic stress disorder (PTSD).
Emma Yeoman's anxiety started when she moved to secondary school.
"I lost many of my friends and attending school became torturous," the 18-year-old says, "Anxiety feels like one of those traps you see in old movies, where the hero is stuck in a room where the walls are covered in spikes. Little by little those spiked walls come in and in, and the escape route gets more and more painful."
At her worst, Emma was signed off sick from "just about everything".
"The idea of getting up and making some toast in the morning made my heart race and my stomach do flips. I lost nearly a stone, a dangerous feat given that my BMI was under 16 already.
"However if my anxiety prison was unpleasant, the escape route was worse. For a large part of my recovery from anxiety, I didn't feel any less anxious. The difference was that now I had to do the things that frightened me.
"This, of course, was utterly horrible. I could make the anxiety go away by quitting and hiding on my own, breathing slowly and avoiding any thought, mention or hint of what was triggering my panicked thoughts. Now I had to confront all of these things, and it was horrible. Giving up, whether on recovery or worse, was an option never far from my mind."
Emma says the only reason she kept up with her treatment was, ironically, because she was worried about quitting and letting her family and friends down.
"I was also anxious about the anxiety getting worse – a comically self-fulfilling prophecy."
"So I was a good patient. I drank the protein shakes prescribed to help me regain some of the weight I had lost, I attended the endless therapy sessions, I even forced myself to go into school and sit, shaking, at the back of lessons I had once enjoyed.
"And what happened? This cruel treatment worked. I inched closer towards a healthy weight, and even closer to a healthy mind."
Although Emma is back seeing a therapist again, she says she is "confident" recovery is well within her grasp.
So how can you support someone with anxiety?
"I think recognising and acknowledging it as a serious problem is important, so not just saying 'pull yourself together', 'come on, why can’t you face it' but accepting and helping them to get help," says McLaren. "I always find it useful to see someone who is having panic attacks with their partner, family member or friend, so then they know what helps, they know what to say when the person starts to have a panic attack and rather than getting caught up in it and swept away in the anxiety, they will be able to have a stabilising and supportive influence.
"Make sure that you understand it and in particular how it affects the person you are trying to support. When we are swept up in a panic wave we lose our footing and believe that we are in mortal danger. Don’t buy into the fear but reassure that they are suffering panic and the wave will break."
What can you do to cope if you suffer from anxiety?
1. Ensure you allow time for relaxation, hobbies and having fun.
2. Try to avoid rushing, doing too much at once or being too competitive.
3. Make sure you get enough sleep at night and take regular exercise.
4. Avoid smoking.
5. Limiting your intake of caffeine-based drinks and alcohol can help reduce anxiety.
6. Avoid cannabis and other illegal drugs.
7. Try making a “problem list”. Then try and tackle the things on it one by one, rather than allowing yourself to be overwhelmed. Ask yourself, “what's the worst thing that can happen”?
Visit the Priory Group's website for more information on anxiety.