None of this is you. You didn't do it. You're not that good. You're not good enough. How did you even get here? Eventually, everyone will see you for what you are: a fake.

Almost 45 years ago, psychologists Suzanna Imes and Pauline Rose Clance coined the term 'impostor phenomenon' to describe 'an internal experience of intellectual phoniness' they had observed in high-achieving women.

So, not just a fraud to others, but even unto thine inner self? That's harsh. You 'fake it until you make it' to the point that it seems like a requirement of the modern MBA curriculum.

But Imes and Clance were seeing successful women who had basically convinced themselves they were only making it because they were faking it. And they would only remain successful if they could keep the pretence going.

It has since become apparent to mental health professionals that this phenomenon - the baseless conviction that your achievements are largely unearned, at best fortunate and at worst fraudulent - is not gender-specific. Some researchers now estimate that as many as 70 per cent of us, regardless of gender, have had or will have a bout of impostor syndrome in our lives.

Impostor syndrome is a recognised mental health issue, but it is not considered a pathology. You won't find it in diagnostic manuals, nor will anyone be offering you a pill to regain your sense of self-worth. Unchecked, however, living with the persistent belief that you're a fraud can be exhausting - leading to conditions that can be diagnosed and treated, such as depression and anxiety.

For some, the experience of self-doubt will only ever be just that: a moment of uncertainty or second-guessing. For others, that experience is a spur to higher achievement: the motivation to work a little harder and keep standards high.

But the flipside of that is over-preparation. You steadily crank up unrealistic pressure on yourself to keep one step ahead of those who might see you for who you really are: a phony.

Impostor syndrome is not limited to doubts about yourself. Given time and opportunity, you may start to question the legitimacy of your entire profession. If you find yourself thinking that your job serves no great purpose, that no one would miss you and your peers if you suddenly vanished from the annals of human knowledge and experience - congratulations - you've got yourself a well-developed impostor syndrome.

At its core, it is suggested impostor syndrome stems from a person's failure to internalise their success. This essentially means that they have not accepted such achievements as coming from their own ability and effort. This, in turn, leads to over-reliance on external factors, like luck or happenstance, as the key explanation for success.

This is palpably worrying on so many levels. It seems some of us are born with low self-esteem; some achieve it (think of our exam-driven education system and the choices it forces on people at a ridiculously young age), and some of us go on to develop impostor syndrome.

But how early does it start? And for