We all need friends - so why do so many of us feel lonely?

How many friends have you got? Do you ever feel lonely? Can men and women ever be friends? What are the benefits of the office spouse? How do you break up a toxic friendship and survive? What are the characteristics of a gal pal versus a bromance?

These are just some of the questions raised by Kate Leaver, who argues in her new book that we are “smack-bang in the middle of the greatest loneliness epidemic in history” and it’s killing us. Loneliness can contribute to dementia, heart attacks, strokes, diabetes and a whole host of problems, not unlike the new science-based findings about lack of sleep. At one point the London-based Australian journalist even claims loneliness is more dangerous than “smoking 15 cigarettes a day and deadlier than obesity”.

Leaver has read extensively, interviewed therapists, academics and scientists, spoken to friends and friends of friends and send out random interview requests on Twitter. Now in her thirties, she combines all this with her own experience of friendship from childhood on. We are told why teenage girls need validation of linking arms while they walk – it’s a form of social grooming – and the value of trading gossip for social status. She interviews Robin Dunbar, the evolutionary psychologist who came up with Dunbar’s number – 150 – which is the maximum number of friends and acquaintances any one person can have, even in these social media-driven times.

In her chapter on friendship break-ups, Leaver clarifies the difference between two friends who have diverged to a point where neither nostalgia nor respect can salvage them, as opposed to the toxic friend who always leaves you feeling drained – though I wasn’t convinced that settling down in pyjamas with a tub of Ben & Jerry’s in front of the TV would necessarily be the best way to “mourn”, and certainly not what I’d “deserve” for getting through it.

Leaver spouts a fair bit of nonsense too. She “cannot think of a lovelier testament to the bond possible between two women” than Natasha and Lynda – platonic friends – sharing the upbringing of Natasha’s disabled child. Nor can she see why a “straight romantic partner would be better qualified for the job,” even though she seems engaged by evolutionary biology.

While conceding that “intimacy between two men is entirely possible” she then disparages the idea of male friendships as often perfunctory and shallow, in spite of acknowledging that perhaps it’s unfair to compare it to female friendship. “It might seem, let’s be honest, inferior to what women have. We’re incredibly loving towards one another. It’s all ‘love you’ and ‘xxx’ and dancing lady emoji.” Speaking for myself, I have never said “love you” or sent a dancing lady emoji to any of my gal pals.

And she has a tendency to gush. Bromance is a “lovely, useful label”, female friendships are “quite simply rather lovely”, as in the sense of the longevity of friendship implied in the decision not to count favours. Late in the book we learn that Leaver has suffered from depression for most of her life, was treated for anorexia at 15, bipolar disorder at 17 and has been plagued by a fear of loneliness all her life, which explains a lot.

American journalist Kayleen Schaefer covers similar ground, although she began her adult life wanting to distance herself from other women in order to be “one of the guys”. A moment of solidarity with a woman at work helped her realise that there were “plenty of smart, funny, warm girls around me to be friends with”. She draws on TV shows and movies, from Dynasty and Dallas to Sex and the City and Big Little Lies, and there’s something nicely sharp about her fascination with the sociological reasons for female enmity and frenemies as much as for friendship.

London blogger Lily Pebble’s book is more of a self-help manual, printed in big type with boxes and bullet points, written by someone whose entire existence is clearly dominated by social media.

Suggestions for what not to do on a first friend date include “Don’t, I repeat, don’t, ask for a selfie on the first date”. She includes comparisons of the best friendship apps and thinks that “offline gestures seem so thoughtful compared to the ease of an online message”.

It is important to disconnect, she urges, suggesting what she calls “The Blackout Dinner” instead where everyone has to put their smartphones in the middle of the table – “no selfies, no emails, no browsing on Instagram allowed. The first one to go for their phone pays for dinner.” How sad, I felt reading this book, that friendship should be constrained by the very medium supposed to enhance it.