The term ‘imposter syndrome’ – originally called imposter phenomenon – was first coined by US psychologists Pauline Rose Clance and Suzanne Imes in 1978.

Clance wrote: “People feel their success has been due to some mysterious fluke, not the result of their own ability and competence. They are also certain that success can’t be repeated.”

Jessica Granish of business support group Alpine Small Business Solutions describes it as “the little troll on our shoulder feeding us lies about our potential”. It’s not humility; it keeps people from acting “because you falsely believe you’re not capable”.

Imposter syndrome expert Kate Atkin classifies it as an intense feeling of intellectual phoniness. This manifests itself in an internal thought process where people ask themselves questions like ‘When will they find me out?” or “If I make a mistake, it will prove that I’ve been faking it all along.”

“It is not a mental health condition,” says Atkin. “You don’t suffer from it; you experience the feelings, although it can cause high levels of stress as you worry about whether you’re going to be found out as a fraud. It isn’t the same as self-doubt, which is perfectly normal for someone starting a business.

“It’s when you have a significant track record of success, you’re highly capable and intelligent, but you still feel like a sham and that soon someone will realise you can’t do this. It’s unrealistic and faulty thinking.”

Imposter syndrome is very common among SME owners. Research from AXA PPP healthcare found that 20% of entrepreneurs feared being exposed as a fraud, being inadequate or a failure – despite evidence proving they were successful. They said it meant they avoided opportunities and taking their business to the next level.

Rob Moore, multimillionaire owner of property networking group Progressive Property, has appeared on live television and shared a stage with celebrities such as Sir Bob Geldof. You’d expect him to be the epitome of a high-flying entrepreneur – confident and ebullient. But you’d be wrong.

“I’ve never felt quite good enough,” he says. “When I started Progressive, I felt very insecure about whether I had the skills to make it a success. I compared myself to rivals and I didn’t feel worthy about meeting them. I didn’t feel credible and never properly marketed myself because I felt that someone would tell me that I didn’t know what I was talking about.”

Karen Green of food business consultancy Food Mentor empathises with Moore. “I set my business up two and a half years ago and wasn’t sure whether I had the capability to do it. This is despite previously being commercial director of sushi supplier Ichiban UK,” she says.

“I’ve got expertise, published a shortlisted business book of the year [Recipe for Success, which was shortlisted for the Business Book Awards 2018] and speak at events. I’ve built my credibility but there’s still in the back of my mind that gnawing question of whether I’m good enough. I know I have unique selling points, but I look at my competitors and think that they’re much better. They have 30 reviews on Amazon and I only have 12.”

Atkin says feeling like an imposter can lead to procrastination – delaying putting a job tender forward, writing a client proposal or speaking up in a meeting – and perfectionism. “If there’s even the slightest typo or mistake, it will prove to you that you’re a fraud,” she says.

Green believes her imposter feelings have held back growth. “Where it affects me most is on pricing. A peer of mine with a similar background charges double my rate. I need to change my mindset on that and understand my value more,” she says.

“It manifested itself in a lot of lost opportunities,” agrees David Ingram, founder of marketing agency Bring Digital, “because I had convinced myself I didn’t know enough to succeed despite a decade of marketing experience. It also kept me quiet at times when I should have spoken up. It’s a tricky situation with clients: they came to me for help and advice, but if I didn’t challenge them on false conceptions or ditch a strategy for one I thought would work better, they’d leave the meeting without anything more than they came with.”

But it can also be beneficial. “The upside is that it keeps you humble and grounded and you work harder,” Moore says. “It certainly helped our customer service. You don’t take things for granted.”

Atkin accepts this point but argues that such a response to the syndrome brings its own extra stress and pressure. “Some people say it fuels them, but wouldn’t it be nice not to have that additional anxiety? Being an imposter is not something we should be feeling,” she says.

So how do you tackle it?

Dr Mark Winwood, director of psychological services at AXA PPP healthcare, says: “Name the self-doubt, acknowledge it for what it is and ask yourself, ‘What’s holding me back here?’ Share your successes with loved ones and don’t shy away from praise. Also, be bolder and take risks. Don’t seek validation from others all the time.”

Atkin adds: “You need to understand the imposter syndrome and recognise it. You need to acknowledge your successes and achievements and the role your skills and abilities have played in that. Don’t put it all down to luck, timing or hard work.”

Moore admits his feelings of inadequacy occasionally still emerge, but he actively takes steps to overcome it. “I’ve stopped comparing myself to other people. We tend to look at people we admire and say you’ve got all the skills that I haven’t. It makes you feel unworthy,” he says. “I also write a list of all my achievements such as awards and profits made. People rarely do that; instead, we look at all the things we’ve failed at or can’t do.”

Green says: “I’ve found that doing positive things like writing the book, getting great feedback after event speeches and customer testimonials reassure me.”

Ingram has also tackled his internal critical voice. “Whereas previously it would be directed at me – “I’m not good enough” – I learned to point that at my work instead,” he says. “What hadn’t I considered in this strategy? What ideas are too safe to really drive the results we want? But the best way to fight it is to stop taking yourself so seriously. I know I’m a business leader and that I have certain responsibilities, but it’s not like I’m the head of the CIA. No one lives and dies by my decisions. It’s that false sense of importance in which imposter syndrome thrives, so break out of it.”