Once, I saw a woman in a supermarket, choosing ice-cream. Of course, I must have seen women in supermarkets choosing ice-cream hundreds of times. I’ve been a woman in a supermarket choosing ice-cream. But not like this.

This woman – small, cropped hair, all in black, a tiny rucksack almost managing to create the illusion of healthy proportion – was choosing ice-cream in a frenzy of extreme mental distress. She would lean over the huge cabinet, her eyes darting over the plastic tubs in terror, as if one of them – she didn’t know which – had the gun that was going to kill her.

Then, she would rotate her head, making sure no one was near, and she’d seize the flavour she had decided on, cradle the carton to her chest and scurry furtively towards the checkout. But, she would change her mind, scurry back to her spot, replace her selection and pace agitatedly away, hugging herself, putting her hands by her sides, hugging herself again. Then pace back. Then pace away. Then pace back and start trying again to decide which – if any – carton of ice-cream to purchase. The poor woman was locked compulsively into making a literally agonising choice.

I knew what was happening. Of course I did. Here was a woman in plain view in a public place, in the throes of a savage mental breakdown. The heft of her guilt, shame and self-loathing was obvious, but I didn’t know how to approach her, or whether it would be wise to try at all.

Strangely, no one else seemed to notice this searingly painful psychodrama. Plus, my toddler son was with me, and my baby. I was frightened of the rawness of it all, the volatility of the situation. I kept casting round, hoping to catch someone’s eye, someone who also saw this girl’s flamboyant trauma, and could help me decide what to do, or – even better – take over the matter themselves. I had no idea how to react in such a situation. I was helpless.

I thought of dialling 999 – this was in the days before 111. But I knew it would be useless. I could start quite strongly, but it could all collapse quite quickly.

“Police and ambulance, please. A young woman – I’m not a doctor and I don’t know her, but I’m sure she has a serious eating disorder – is having what looks like a psychotic episode in Sainsbury’s on Clapham High Street.”

“A psychotic episode? But you say you’re not a doctor. Is she a danger to the public? Can you describe her behaviour?”

“She’s having a lot of trouble choosing ice-cream.”

Then – third time lucky – she strode all the way to the checkout, bought the ice-cream and left the supermarket, taking all of her considerable troubles with her. All I could do was hope she had good support from her family and friends who loved her, and access to mental-health services that knew what they were doing. People do recover from eating disorders, mostly. People are also killed by them. Far too often.

This week, we’ve learned that people with eating disorders can wait up to 182 days for mental-health treatment in some parts of the country. This is a catastrophe. But this is not a piece about what causes eating disorders and what needs to be done to stop them. There are plenty of the former, and the most immediate solution to the latter is so often stated in the wake of shocking news items such as this one that it is in danger of becoming a tired trope: vastly improved mental-health services is priority number one.

Instead, this just a piece inspired by young people with eating disorders that I’ve encountered, often through their parents. Parents often feel the same fear, impotence and – yes – frustration that I did in that supermarket, but with a hundred times the intensity, a million times the involvement. They bear it, they fight it. They coax their children out of it, with the help of professionals who know what they’re doing. Mostly. Some statistics suggest that as many as one-fifth of anorexia sufferers will die a premature death linked to their illness.

It’s established that perfectionism or high achievement is often a trait implicated in anorexia. And maybe it’s just the middle-class circles I move in, but what I notice about young people who fall victim to eating disorders is that they’re very often people who have complex, dazzling choices.

A boy who was struggling to choose between a very promising career in film-directing or a very promising career as a musician. A girl who could have gone pro at tennis, was also being doggedly scouted for modelling, but had opted to study medicine. Kids so academically gifted that an A without a little asterisk after it feels like failure. A teenager so young, so clever, so beautiful, so savvy, who has all the money, freedom and opportunity in the world.

I’m not saying rich, difficult choices are all of it. I’m not saying they’re necessarily even part of it. But because I saw that girl, crippled by the terrible torture of ice-cream selection, I can’t help looking for the choices in the lives of people with these dangerous, terrifying eating afflictions, and I always find a plethora of creamy, delicious, intense options sitting there waiting to be accepted or rejected. Anecdotally.

There are so few generations who expected their lives to be much as their parents’ lives had been – especially among girls, who had very few choices at all – and populations who feel under pressure to make the most of every opportunity, and thereby invent for themselves an amazing, exceptional life. Or fail to. I may not know much about the psychological twist and turns of eating disorders. But I do know one thing: the contempt this society has for failure – or for so-called failure – is toxic, utterly toxic.