Santaholics Anonymous, by Scarlett Thomas

For weeks we've been exhorting you to spend, spend, spend, but now that the presents have (with any luck) been bought and the preparations are complete, it's time to ponder the deeper meaning of Christmas. We asked our favourite writers to rant, reflect or reminisce on a festive theme. As Ronald Hutton explains, the last thing you should feel at this time of year is guilty, so sit down with a mince pie and enjoy

There are several recognised ways of confirming that you are officially an addict, beyond simply asking yourself, "Do I do this too much?" and "If I keep doing this, is it likely to kill me?" You can ask yourself a whole range of questions about your bad habits drinking, smoking, gambling, downloading naughty pictures, or whatever. Key questions are: "Do I feel guilty afterwards?" and "Do I think I can stop, even though I can't?" Other key signs of addiction include missing work or school because of your habit, and its effects on your family life. Addicts commonly try to recreate the first time they enjoyed something, and often engage in ritualised behaviour around their addiction.

It would be comforting to think that our familiar British Christmas differs structurally from this, but I'm not sure it does. This year, as November drew to a close and it became, again, impossible to go out and buy something simple, like a tube of toothpaste or a bagel, without having to listen to Slade at the same time, it struck me that Christmas is in fact horribly like a mass addiction. It's bizarre: every year virtually an entire society starts behaving the same way, mainly shopping and worrying, and there's nothing joyful or celebratory about it.

People become obsessed with ticking items off lists, and making sure they've got "enough" for Granny. Will the table look like the one in the Sainsbury's magazine? What can you buy for the man or woman who has everything? Of course, in our world of sweatshops and consumer credit, almost everybody (well, the "everybody" who reads newspapers like this) already has almost everything they want. But at Christmas no one admits that. We're in mass denial about what we're doing. Weekend supplements run pages and pages of "gift ideas", because in the downward spiral of addictive behaviour, there is no such thing as "enough".

Yet another sign of addiction is feeling disgusted with yourself afterwards, and, in the later stages, actually feeling miserable while you do the thing that used to make you happy. I've noticed that it's not just me who hates Slade, Band Aid, Wham! and all the other crap that blasts out of every shop, every single year. Everyone seems to trudge around feeling (or at least looking) miserable, probably because they know that, come January, they will be faced with cold, dark winter nights and a huge overdraft.

You can, of course, go home and watch some uplifting American film about the spirit of Christmas and everyone being kind to one another. But when you're in Debenhams or Sainsbury's and you're only two items into your massive list and you haven't even thought about the milkman, the postman, the cleaner or whether you should get a stocking as well as a turkey terrine for your dog/cat, you probably feel that the equally harassed woman who's just bumped you with her overflowing trolley can stick the Christmas spirit up her fat arse.

One of the reasons addictive behaviour starts to feel "wrong" and "guilty" is that addicts soon begin to dispense with all but the pure centre of the addictive pleasure. Many people will understand how the few glasses of wine with a good meal can turn into quite a lot of double shots without food; and reading erotic novels can sometimes mutate into fast-forwarding to the penetration scenes in hardcore porn films. So we can also recognise why the baby Jesus doesn't feature too much in our British Christmas any more. In fact, screw the baby Jesus and his entourage and midnight Mass, holly, ivy, mistletoe, carols and hoping for snow. Forget sending Christmas cards: we're all too stressed. Bring on the presents! And switch on the TV! The main point of Christmas now does seem to be an orgy of consumption, with, like all orgies, a climax that in the end leaves you feeling hollow rather than fulfilled. Calls to the Depression Alliance helpline go up by 40 per cent over the festive season, and one of the reasons is apparently that people become overwhelmed by having to make the occasion feel "special".

It's always hard to talk about addiction, partly because it involves admitting that you have given yourself up to pleasure. It's not that people don't moan about Christmas, but it does seem a bit obscene to admit having trouble coping with your own overconsumption and excess while half the world starves. Knowing this, many people experiment with the Christmas equivalents of decaffeinated coffee, mocktails or Nicorette gum: Fairtrade presents and "good gifts". Then they sneak in a DVD recorder and a new laptop as well. Why does this happen? Why can't people give up their full-strength Christmas?

Perhaps, like the addicts we are, we are all lost in a nostalgia for something that never really was. If you're lucky, when you were a child there was such a thing as an uncomplicated Christmas. But that was because someone else bought the presents and made the lists and roasted the turkey, and you probably got what you wanted, because all you wanted was a new bike and a couple of Famous Five books, and no one bought you a pair of knickers three sizes too big, or a menstrual calendar for a Filofax quite a lot smaller than yours. Or maybe there never was a perfect Christmas, except for the ones you once read about in books, and continue to read about in magazines. Most harmful pleasures have a glamorous image more powerful than the painful reality: it's often why we start indulging in them. After all, the Marlboro Man never seemed ill.

Once you realise Christmas is an addiction, you see that it even has negative effects on local communities. Is there such a thing as passive Christmas? Every year, when I can find time to stop pitying myself, I spare a thought for those people who don't celebrate Christmas but who can't escape from it. It's not just that buying a loaf of bread becomes almost difficult in mid-December, but Christmas is inescapable on TV, in newspapers, on the radio and in most institutions. However much we buy into the idea of goodwill to all men, Christmas becomes the most bleak time of year for people who need attention but can't get it because everyone's so busy buying presents.

But I'll admit it. My name is Scarlett Thomas and I am addicted to Christmas. Every year I say I'll give it up, but I don't. My mother also tries to give up, but she can't do it either. In some ways it's just like smoking.

After everything I've just said, I probably should be declaring that this year I will be working for a charity (as I did, sort of, in 2002), or knitting all my presents (as I attempted last year). But in fact I'll be trying, like most other people I know, to enjoy being a non-Christian using a Christian festival as an excuse for a holiday and some nice food.

Is the solution simply to admit this? Probably not. There's so much wrong with Christmas that no one will ever solve it. It should be banned for all our sakes, but it probably won't be.

So despite moaning about it until about 15 December, I remember how much I like giving presents, and the taste for it all comes back. I'll believe that maybe I can become a functioning addict, and get the pleasure of Christmas without the hangover, the overdraft and the need for emotional rehab and/or a lot of winter Pimm's. It must be possible. But then, to be an addict is to be an optimist: to seek pleasure without pain and think that the impossible is possible. And it's only a 12th of my life.

Scarlett Thomas' latest novel is 'The End of Mr. Y' (Canongate)