Some time ago, Elsa Godart - a French psychoanalyst and philosopher - treated a young girl who had taken semi-naked pictures of herself that went viral. The girl was distraught (the pictures were intended for her boyfriend alone) "and it all came down to this momentary lapse of consciousness", Godart explains, "a moment so powerful that all critical thought was suspended - along with any common sense. I found that fascinating."
Once she began to delve deeper into the apparently anodyne and playful world of selfies, she found repeated (and sometimes fatal) instances of these "critical black-outs". Last year, more people were killed taking selfies than in shark attacks, for example (a number of those in the Philippines, the "selfie capital of the world").
"People are forgetting there's a cliff behind them, or getting squashed by trains. And those aren't the only aberrations: people are taking smiling selfies of themselves in front of Auschwitz and with dying tramps in the street. Last summer a British parliamentary candidate took a selfie on the Tunisian beach where 38 tourists had just been gunned down.
"And at Nelson Mandela's memorial service, David Cameron, President Obama and the Danish prime minister forgot where they were long enough to lean in for a selfie. So I became obsessed with finding out how one can lose consciousness to that extent."
Godart is far from alone in her concerns over the selfie trend: at last weekend's Vogue Festival, psychologist Dr Tanya Byron warned that sexualised, unrealistic images posted by celebrities were fuelling depression and eating disorders in young people.
In Godart's new book Je Selfie donc je suis (I Selfie Therefore I Am), she examines a society she describes as being "stuck in a state of adolescent crisis". Far from giving us a stronger sense of our own identities, she insists, the one million-plus selfies taken every day across the world (the average Millennial is expected to take 25,700 selfies in his or her lifetime) will only propagate insecurities and provoke precisely the kind of neurotic and self-questioning behaviour that characterises adolescence.
"We all now have very limited attention spans and very little patience," Godart says. "Only we forget that adolescence isn't a very enjoyable time: we don't know what we stand for or where we're going, and we're in a state of crisis, just as society is now."
Selfies are often lamented as a symptom of narcissism - indeed, last week a study found people who take them tend to overestimate how good-looking they are - but she says that's not the major problem. "Narcissism isn't always bad," says Godart, who admits she's fond of taking the odd selfie herself. "In fact it has a useful side: it's necessary when we're infants who start out life mesmerised by our own image in the mirror. Small children are literally their own love interests: they find jubilation in pictures of themselves."
Not unlike Kim Kardashian or Miley Cyrus, then, who seem to be locked into the "mirror stage", and drawn to any reflective surface in much the same way as my daughter was as a toddler? "Actually that's more a case of egotism: the cult of 'me'," corrects the 37-year-old Godart, who is a stickler for clinical terms and looks - perhaps inevitably for a Parisian philosopher - like Isabelle Adjani.
At the heart of the selfie is a contradiction, Godart explains in the book. "What may look like straight-forward narcissism can often be insecurity and a craving for reassurance that you can only ever get from 'likes'. But you're chasing the dragon, because far from calming any neuroses down (although it may do this for a second), posting another selfie will only amplify them."
This may explain extreme cases such as that of Danny Bowman, the British teenager who was treated for body dysmorphic disorder and suicidal thoughts in 2014 after ditching school, locking himself in his room for six months and taking up to 200 photos a day in a quest for the perfect selfie.
So, is Godart really trying to say that Kim Kardashian does what she does because she's insecure? "In her exceptional case," Godart says wryly, "maybe not. With Kim it points more in the direction of an identity crisis."
Although the psychoanalyst worries about the number of young girls and boys she sees professionally "caught in a social media and reality TV-fuelled obsession with marketing themselves as a product and selling themselves to the world", Godart is not in the blame game. "I'm not here to judge or say that this is down to any one celebrity or public figure in particular, because they're all doing it: just look at the Pope, the Queen and Obama.
"But where it becomes worrying is when the illusory virtual self you're selling is more appealing than the real self. So you can Photoshop yourself into your ideal and of course that illusion is so perfect that nobody wants real life any more, where you actually have to work really hard to get anything done - or look a certain way. So I could lounge around like a slob all day at home," says Godart, "while constructing this shining virtual image of myself online, and that's going to paralyse my actions in real life, because I can never get anywhere near the perfection of my virtual life."
It's that disparity, along with the isolation of selfie-taking, that concerns her most. One study in the book shows that the more selfies people take, the less sex they have. "It makes sense that the more time spent on oneself in a virtual world, the less open one is going to be to others in any capacity - but certainly sexually." There's even a site - beautifulagony.com - where people can post pictures of their faces at the point of orgasm, doing away with any need for a sexual partner.
"So although selfies can be anodyne and fun, there is a real danger of us losing our connection to and consciousness of the world around us. I'm not here to make moral judgments; all I would say is this: spend 10 hours a day on the internet if you want, but be capable of going beyond that screen in life, because otherwise what you're really losing is your own freedom."