Super stress: crumbling under the pressure of the economic crisis

But for a senior banking executive, as Don (now 60) was, that worry was strong enough to keep him awake at night - and from 2007-2008 he never slept more than an hour or two a night. It was the first sign of the super-stress that is spreading among City workers and which last week caused Lloyds Banking Group chief executive António Horta-Osório to take leave of absence.

"There has definitely been an increase in City workers suffering from stress, and the context is very much around job insecurity and increased pressure," says Dr Andrew Parker, a consultant psychiatrist at Capio Nightingale Hospital in Marylebone.

Capio has just announced plans to open a specific stress and post-traumatic stress disorder clinic to deal with the increasing numbers of people with stress-related disorders - now the most common cause of sickness absence from work in the UK.

"At the more senior end, people are finding themselves in impossible situations, having to make redundancies or hold on to information that they can't talk about," Dr Parker says.

"People do feel traumatised by events such as losing a lot of money on the markets and that can become very much like a post-traumatic stress disorder, where the key symptom is being plagued by intrusive thoughts and memories of the event."

But initial signs of stress are not always obvious. "Sleep loss was the only symptom I was aware of. I was still functioning well, keeping going on adrenaline and coffee," explains Don. "City workers can go for a long time with symptoms of stress, which they are probably not aware of," confirms Dr Parker. "Many have personality traits that can be broadly classed as obsessional - perfectionism, high standards, attention to detail. They also tend to be people who may not be so flexible when things go wrong and are not so in tune with their bodies."

It was only after a year of sleepless nights that Don approached his GP and, much like Lloyds CEO Horta-Osório, was told he needed to take time off. Yet time off is not always the solution.

That work, and staying in employment, is good for mental health is the clear message from the Centre for Mental Health.

Sharon De Mascia is a programme manager at the charity that trains employers to identify the early warning signs of stress-induced anxiety and depression in their workforces: irritability, impatience, poor concentration, social isolation and heavy drinking.

"Managers should encourage the person to seek professional help, but at the same time look at what support and adjustments can be made in the workplace to keep the person in their job," she says. This might mean moving a previously customer-facing employee to a back-office role temporarily until a prescription of antidepressants has started to take effect, for example.

Don's experience highlights this need. "Unfortunately, when I stopped I became what would be characterised as depressed - anti-social, exhausted and fed up. There are many like me in the City, for whom work is life - it's your hobby, it's your interest. The removal of work was traumatic. Your life crumbles and suddenly you lose your route to recovery. A lot of people in my situation commit suicide."

Yet there's still a huge stigma in the City attached to seeking help from a mental health professional. "If you talked about cognitive behavioural therapy, people like me would just cringe and say 'I'm not doing it'," he says. So for Don and City workers like him, that means getting reassurance that therapies can suit people "used to self-motivation and a series of deliverables and objectives".

Don was referred to Capio Nightingale. "The person I saw was not patronising. There was no Freudian analysis or junk or childish behaviour," he says.

Dr Parker recognises this attitude. "People find it hard to equate that as a highly intelligent person they are at the mental health clinic seeing a psychiatrist. It's very important that you meet them on their level. I sometimes see people at their offices or in coffee shops."

"I was hugely relieved," says Don. "I went once a month and we talked about the financial crisis. It was like going to meet a friend just to check that each month you're significantly better than the previous month."

Vitally, stress-related disorders are not permanent. Don did leave the bank he worked for but took up independent consultancy work and now says: "I feel absolutely fine. This year I have been extremely busy, I've enjoyed it and earned lots of money. You can imagine that António [Horta-Osório] had so much on his plate that it was just one big worry, but you can also imagine that soon he could be fine again."