We used to know where we stood with the midlife crisis. Usually a speciality of men approaching their mid-forties, it manifests itself as a cringeworthy physical makeover, the purchase of an unsuitable car and the amorous pursuit of a younger woman with whom to have bendy weekday sex. There’s still plenty of that around, of course (step forward Liberal Democrat MP Lembit Opik), but there are signs that this period of dramatic self-doubt is striking us much earlier. If you’re in your mid-thirties, hassled by the dramas of juggling work and family, doubting decisions you’ve made professionally and personally, panicked by the ageing process and dismayed that your years of snogging in nightclubs are behind you, then you’re probably in the grip of an early midlife crisis – otherwise known as a thrisis.

Perhaps we shouldn’t be too surprised, given our accelerated pace of life – kids drinking alcopops at 13 and reporting signs of burnout before they turn 18. Little wonder that, by 35, many of us feel exhausted, not to mention a little nonplussed about what’s next. Gladeana McMahon, co-director of the Centre for Stress Management, knows the phenomenon only too well. “I work with a lot of highly successful, driven people,” she says. “By their mid-thirties, a lot of them are tired. They’re sick of life and they wonder what it’s all about. They start questioning their values and what they’re doing.”

The frantic, permanently “on” nature of modern life does not help, what with our crackberries and multimedia homes. “We don’t make the distinction between work and play any more,” McMahon says. “It’s hardly surprising that you get to 35 and think, ‘Blimey, is this it? Am I just facing more of the same?’ ” Nobody tells you about this in your twenties, when you’re determinedly marching up the corporate ladder and seeking a soul mate. There are angsty moments, of course, when you come to terms with the harsh reality of living in a grown-up world and having far less time to sit around eating Pot Noodle and watching Neighbours, but there is comfort in having a clear path to follow. It’s just a lot shorter these days: 20 years ago, it would have taken us at least two decades to get to the top; now, in our increasingly ageist culture, we want it all by 30. The knock-on effect is that, suddenly, bang, you get to your mid-thirties, you’re already a partner in your law firm or one of those “vice-president” types, and it occurs to you that there is nowhere else to go, other than buying the company.

Will, a single 35-year-old former banking executive, was so depressed by the notion that he has handed in his notice and is off to join VSO. “I just want to do something – bloody anything – to stop the rot setting in,” he says. “I’ve spent years working my way up, but all I want is to feel some adrenaline again. There’s nothing like turning your back on a £250,000-a-year salary to get that.”

Two of my female friends also threw in big jobs as their 35th birthdays approached, and not just because of the stresses of juggling work and motherhood. Rebecca, 35, explains her decision to walk away from her position in a prestigious publishing firm: “The working-mum thing was part of it – I was stressed all the time – but there didn’t seem to be anything to work towards any more, just more of the same annual milestones.”

Another friend, in a reversal of the cliché, threw in the towel on the nice husband she had married at 29 just before her 35th birthday. “It wasn’t him,” she insists. “I just found myself sitting across the breakfast table from him, thinking, ‘Is this it?’ It was getting to the point where we were going to have children, and I thought, ‘I’ve got to get out.’ I felt stifled, old before my time. I literally couldn’t bear the fact that I would never feel the excitement of a first kiss again. It hadn’t bothered me when we got married, but it bothered me then.”

This is perhaps less usual at my friend’s age (lots of us don’t even get married until we’re 35), but it’s an example of the way our mid-thirties have become a flash point in both our professional and personal lives. A recent survey revealed that midlife crises are now the second most commonly quoted reason cited to divorce lawyers as the cause of marital breakdown.

A thrisis can easily afflict those who have seemingly ticked all the boxes. A couple of people I know, robust types who would have turned up their noses at the notion a few years ago, have recently turned to counselling in a bid to tackle the sense of boredom, even futility, that has gripped them, despite their success.

In this sense, the thrisis, however real it feels, is rather indulgent. The big question is whether it is simply additional to, or replaces, its older relative. Or are there now two hits, one at 35, and another at 45? If so, to borrow the sentiments of the redoubtable Lady Bracknell, to have one midlife crisis may be regarded as a misfortune – but to have two looks like carelessness.

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