My first best friend S was the Queen Bee of my tiny primary school class. She was as glamorous as any young girl could possibly be, with huge blue eyes, unusually long eyelashes and silky long brown hair that her equally beautiful mother pinned with Japanese kirby grips each day. This was the 1970s and anything from Japan conveyed the height of sophistication. She also had stationery bought from half-term trips to France, and a red leather school-bag that never scuffed. I was besotted.

S called all the shots: what games we’d play in our free time in the playground, and also who we liked or didn’t like. E was a wimp, J was too swotty, but my nemesis N was the one I sweated over. Sometimes she was awful and to be ignored, but then other times, seemingly at random, she’d be promoted to become S’s favourite, leaving me confused and hurt. The ostracism usually wouldn’t last too long and N would be relegated again, leaving the seat warm for my inevitable, dogged return.

But then one day, after a very long patch of being S’s number one, I skipped into the changing room at school to change for our weekly games lesson. S was there already, sitting on a bench in her pristine white airtex and shorts, while N looked adoringly at her from her side. S caught my eye and swiftly swivelled her head, and then her body, away toward my contender. Desperately hoping this to be an error, I sat down beside Stephanie and began to chatter. Turning back toward me, she used both of her olive-skinned hands to press firmly against my thigh to slide me away. I was never her number one again.

I’m lucky in love. No partner has ever come close to breaking my heart, but S succeeded. The betrayal cut so deep, that even twenty years after her rejection, when I spotted grown-up S at a friend’s wedding party, I had to leave the room to collect myself. That friendship helped to set the tone for ones to come too: I have worked hard to build and maintain many friendship groups, and to be a good friend to as many as possible. By hedging my bets, and spreading bonds far and wide, the chances were – and are – there’d always be someone that would like me.

I know I’m not the only one who invests a lot of time, energy, money and emotions in friendships – partly because ‘birds of a feather’ applies to some of my closest, but also because in my work in the consulting room, I spend most of my waking hours talking to adults about their lives, along with the relationships that figure the most in them. Friendships matter, and sometimes they matter a lot. They may make us, break us or re-configure us in positive or negative ways.

The science of friendship also tells us that healthy bonds with non-family members are protective of physical and mental health. Just as eating well and exercising help to prolong our lives and improve their quality, we now know that our connections with others are just as important, if not more. Robin Dunbar’s work in the field over the years has pioneered this thinking, and emphasised the dire effects of not having friends – loneliness is finally being recognised as a health factor in society too. But despite all of this, we don’t tend to give them the airtime in the consulting room as compared to other relationships, especially in adulthood which is the time when I talk to clients.

If my clients refer to friendships at all (most usually women who tend to experience more intense friendships than men), they tend to easily dismiss them as important, as if such bonds aren’t important enough for the ‘serious stuff’ of therapy. The lingering effects of childhood friendships, and the contemporary upsets caused by adult friendships are often deemed ‘silly’ or ‘childish’ and waved away with a hand. This is partly to do with the fact that, unlike other relationships, we don’t have clear rules for the engagement, maintenance and extrication of friendships. You may consider going to therapy after a break-up with a partner, but less likely after a fall out with a lifelong friend.

When we ‘pair bond’, the rules are vaguely clear, although attempts have been made to nail some down in best-selling books. Generally though it’s fair to say, we meet another, we flirt with each other, then get together or not, and if we do, we may then try to make a relationship last. If things work out, we may seal the bond by setting up a home together or getting married or having a child. If things don’t work out, we separate and decide if and how to have a relationship again. In the case of a legal separation of divorce, the law steps in to guide some of the parameters of the next relationship. But when friendships go awry, we have fewer set ideas and we muddle through, sometimes with great, and underplayed, distress.

Therapy tends to cluster its thinking around the centrifugal force of early attachment relationships: mothers, fathers, siblings, extended family members. And as we grow up, relationships with our most intimates – our partners and children – become inflected with these blueprints from our early formative relationships. In other words, our ‘attachment style’ in adulthood derives from how we were cared for, and how we responded to that caring. Friends don’t get much consideration in theoretical discussions, nor in the popular mind of what therapy is about – but they are affected by our early imprints too.

My childhood heartbreak is not unusual, and I think it’s fair to say that female friendship can be particularly fraught with anguish as compared to male friendship. In therapy, I take it seriously when friendships affect us in similarly powerful ways: filling gaps of yearning and desire to our detriment, breaking or mending our hearts and minds, or even existing in our minds only as a means to survive in a lonely world. Much of this exploration depends upon how we define friendship of course, which can reach to the heart of many matters in the first place.