There are some kinds of depression that even chocolate can't cure, and when Helen Birch feels down, she heads for the high street, where relief, even if te mporary, can be found wrapped in tissue paper
"New York, just like I pictured it, skyscrapers and everything," giggled my friend Stella as we strode down Fifth Avenue towards the huge, glittering snowflake fashioned from 3,000 fairy lights, suspended like a beguiling star of Bethlehem above t he hallowed halls of New York's poshest shops.

After a few of hours schlepping up and down this Materialist Mile we had to remind ourselves that we hadn't come just to shop. We staggered through stores festooned with designer decorations and pre-Christmas discounts that made my flexible friends turn somersaults.

It was all so beautiful, so tempting, such an artful way of teasing out unbidden desire, but I felt the tiniest pang of guilt when I rushed out to make a final purchase - another bag to carry back presents for my family and friends that, one for one, I'dmanaged to match with just a little something for myself.

This was a feel-good expedition, an exuberant spending spree. A healthy response to the vibrating finger of capitalism. But the prospect of shopping is never so compelling as when I'm depressed. A few years ago, after ending a particularly brutal, long drawn-out relationship (he was the brute), I got drunk and went to bed for the best part of week. When I got bored with watching TV and leeching my friends' sympathy, I got up, went to the opticians to be fitted for some contact lenses and hit the shops,intent on frittering my remaining overdraft.

Not that there was anything rash about my purchases. First stop, Jigsaw and a silk Equipment shirt rip-off, carefully chosen for colour and texture and long enough to hide my rapidly diminishing bulges. Food, a comfort to so many women afflicted with gloom, no longer held much allure for me. Then it was Oasis, Whistles, Miss Selfridge, Bertie, Hobbs, Boules.

Mindless of the robust ticking off I'd get from my iron-maidenish bank manager, I returned home, loaded with carrier bags, their contents caressed by tissue paper, feeling better than I'd felt since, well, the last time I'd gone shopping (this really wasa grim relationship). Kitted out in a new coat of armour in the form of said silk shirt, leg-lengthening trousers, and a fresh application of warpaint on my lips, I felt ready to face the world again. Hell, if I was going to bleed, I would at least bleed from the lip with the illusion of a drop-dead pout.

This fooled enough people into believing I was handling it all quite well. I could almost believe it, too. Which made a difference. My confidence might be in rags, but the surface was beautifully stitched together. I knew that parting with all that cash was simply an exercise in self-manipulation, but I had bought self-esteem off the peg. If I could look good, then maybe I could feel good again, too.

Of course, all this was just a quick fix. Soon I was hauled into the bank manager's office like a sulky schoolgirl, having to scrabble around to meet that month's rent, and depression cast long shadows again.

Some women, like my friend Stella, have more sense than to collapse on to the retailer's couch when crisis strikes. They say that shopping when they hate themselves makes them hate themselves more. They feel fat and ugly and they think that everything they try on makes them look even more horrible.

But many women and, if my straw poll of male acquaintances means anything, an increasing number of men, find fleeting solace in their purchasing power. Another friend confessed a weakness for buying expensive silk lingerie when she's depressed. She hidesit in her cupboard when the inevitable attack of panic kicks in. But, like illicit sex, it gives her a frisson of pleasure knowing it's there.

Some people experience depression shopping as less an exercise in therapy than an act of punishment. One colleague said that when he feels depressed he buys stationery, and that he now has more pens and notebooks than anyone could use in a lifetime. The purchases give him a sense of new beginnings, but once he adds them to the piles of others he knows he'll never use, he feels guilty and acquisitive. At least he could afford to flagellate himself. Sara, a single parent, used to spend £200 on a pair of shoes to cheer herself up, then come home to find the fridge bare and the next pay cheque somewhere over the rainbow.

Excessive though it can be, there is a difference between therapy shopping and shopaholism, the latest female affliction to be endowed with a pathology, a helpline, a course of special anti-depressants and a 12-step programme no doubt coming soon to a venue near you.

And it's not just one of degree. The shopaholic is gripped by an insatiable desire that turns her once-reliable flexible friend into a fickle temptress who threatens herself and her family with bankruptcy. But the consumer of shopping therapy knows its limitations.

This week, Britain's high streets will be packed with women shoppers not only looking for a bargain, but out to give their self-image a shot in the arm. They know that they won't get out without paying, in Geld and guilt, but they also know that when you're down, keeping up appearances can be a girl's most effective weapon.