Is anyone genuinely surprised by the findings of this week's report suggesting that mindfulness based cognitive therapy (MBCT) is effective in treating depression and anxiety? Almost four years ago, I went to my GP, Jonty Heaversedge, because the anxiety that had dogged me all my life had reached a frightening level. Jonty – who, serendipitously, happened to have written a book about mindfulness – got me a place on a six-week, NHS-funded MBCT course at the Maudsley hospital in south London. And – there is no less cliched way of saying it – that course, and the meditation practice I've done every single day since, changed my life.

I was always an anxious child, hurtling from one terror to another. I was afraid that the house would burn down. Or burglars would come. Or that a dress my mum liked me to wear would suffocate me as it was pulled over my head. For as long as it fitted me, the presence of that dress in my wardrobe haunted me.

And it didn't stop there. Darkness, water, wolves and ghosts, illness, poison and death. Standard child fears, perhaps, but I devoted serious time to them. Afraid to sit on toilets in case a rat emerged from the U-bend, at school I also had to leave the cubicle door unlocked for fear of being accidentally locked in all night. A book that showed Joan of Arc burning to death at the stake had to be put on a high shelf – though I still had to work on not glancing up at the shelf. I bit my nails. I joggled my legs. I jumped when the toast popped up. At night I would lie awake and stroke the dark nylon fur on my panda's nose and whisper to him that everything was "all right". But who was I trying to reassure – him, or myself?

If I sound like a miserable specimen, there were upsides. A fierce and (to me, anyway) entertaining imagination, a sense of humour (I never minded being laughed at) and a healthy dollop of optimism meant I would have called myself happy. Which, largely, I was. I quaked and hoped and goofed through my teens, emerging into adulthood as someone who gave a good impression of being, if not exactly relaxed, then able to cope. Getting through university, working in the theatre, falling in and out of love and then, finally, having my babies and even achieving my dream of becoming a published writer – all of these were actively happy experiences that, in some vital manner, calmed me down.

"Why are your novels so dark when you're so bright and happy?" people sometimes asked me. I understood the question – but the answer? Wasn't I just lucky to be allowed to explore my deepest fears in fiction, a safe place where I dared to peer over the edge of the abyss, and could even use what I saw there? This saved me from being a neurotic, anxious pain in the neck – didn't it?

I had a blip in my 30s. Writing my third novel, with three small children, a supportive partner and a mostly calm and happy life, I woke one dark middle of the night gasping for air. The fear was inexplicable and intense. Over a few months, I had several episodes of tachycardia (an abnormally fast heartrate), one time ending up in A&E because my heart would not calm down. Finally, given a totally clean bill of physical health, I was asked if anything was stressing me. I had recently trained as a counsellor for Childline, and some of the calls were grim. It was suggested that I stop and, reluctantly, I did. And so did the tachycardia.

And then, of course, my late 40s. A few years of intense stress over drug-taking in our family, followed by a sustained attack by the press on the book I had intended as an honest discussion of that subject. Overwhelmed by guilt and responsibility for the damage I'd inflicted on those I love, I started to believe everything I'd been told: I was a Bad Mother, a Bad Person, a Bad Writer – my every reason for existence undermined. I stayed as strong as I could while the storm raged, but months later, when it had all subsided, I fell apart.

I drove off shopping one morning and, only yards down the road, was overwhelmed with panic. My husband had to come and rescue me. I tried to shake it off but it happened again and again – once, scarily, causing a minor prang on a country road (to the kind man in the Volvo with the labrador in the back: despite your protestations, it was my fault and I'm sorry).

Appalled by this untrustworthy and – surely? – dangerous new self, I proceeded to lose my nerve about everything else. Live TV and radio, something I'd previously loved, seemed suddenly fraught with risk. What if I felt trapped and had to tear my microphone off and flee the studio? Theatres were unbearably claustrophobic; cinemas barely less so. I could not even think about the tube. Buses had seemed a gloriously safe alternative to cars, but I found myself watching the doors between stops just in case. In the classic mode of chronically anxious people, I began to avoid all situations that felt threatening. Stranded in a sea of possible triggers, the piece of land I was standing on – clinging to – grew smaller and smaller. It was when I realised I could not even ride the escalator in John Lewis without a mounting panic that I knew I had to get help.

Which is how I found myself sitting in a circle in a small room at the end of a long corridor at the Maudsley one rainy Tuesday evening in January 2010. Two reassuringly stern yet affable psychiatrists in suits – Dr Florian Ruths and Dr Stirling Moorey – faced 20 or so of us, and guided us through a series of exercises.

I think we lay on the floor and did a 45-minute "body scan" meditation. It was uncomfortable, boring and a bit embarrassing. My foot itched. One or two of the men dropped off and snored.

The first sitting-down meditation was excruciating. A whole 40 minutes sitting in a chair and doing absolutely nothing, while Dr Ruths talked us through it. I was bored, restless and (of course) had to fight an impulse to run from the room. As we sat in our circle and shared the reasons that had brought us all there, my memory is that I was the only one suffering from anxiety (as opposed to depression), and also that I definitely came across as the "maddest" – there was no one else in that room who had trouble staying on a bus.

Some people in the group shared expansively, some less so. One or two never spoke. But the sense of kindness, openness and acceptance was inspiring and comforting. We were sent home with daily homework: progress sheets to fill in and various guided meditations on CDs. I did mine diligently – I wanted, very badly, to get better. But I was also beginning to remember why I'd resisted the idea of meditation for so many years: it was difficult, dull and uncomfortable. What was the point?

Quite how this changed – but change it did, and profoundly so – is hard to say. Somehow, somewhere, across those six weeks, something happened inside me – in my head? my body? my soul? – and I began to understand. Sitting still became a boon and a comfort, even a luxury, rather than a threat or an irritation. And the present moment, right here, right now, began to seem a very comfortable (and comforting) place to be, bereft of dread and full of the possibility of peace and calm.

Most importantly, I seemed to be developing a whole new relationship with my thoughts. It wasn't that they'd really changed; they were still the same old wolf- and fire- and death-fearing thoughts, but I could see that they were simply that: thoughts. I did not have to judge them, act on them or indeed do anything very much about them. Sometimes they were interesting, sometimes less so, but they were no more than "events" that arose in the mind and then dispersed again. They did not, as I'd previously imagined, have the power to undo me. Only someone who has suffered from chronic, debilitating anxiety will understand quite how exhilarating this realisation felt. I had made peace with the workings of my mind. I was no longer afraid of myself.

It didn't feel as if I had done much to make this happen, apart from turning up and being prepared to sit there. But that, of course, was everything. Still, it felt oddly effortless, as if something in my head had been subtly rerouted. And it turned out that there was far more space in there than I'd ever realised. Like finding a whole new room in your home that you never knew existed (imagine the excitement), I could wander around my mind and luxuriate in the boundless space.

Once the course was over, I continued – and still continue – to meditate. Every day, without fail (after coffee but before getting dressed), I sit, usually for 10 minutes, or if I can, for 20. Sometimes I love it. Other times it feels harder. Now and then, the capricious cacophony of my mind still amazes me: all those thoughts and worries and ideas and fears swirling around in there.

But the point is that it doesn't matter. As our teachers memorably told us, there is no such thing as a "bad" meditation, apart from the one you don't do. Mindfulness is not about trying to change things, but accepting them as they are, non-judgmentally, with as much kindness and gentleness as possible.

And I now do just about everything I had ceased to be able to do. All right, driving on fast roads still eludes me – but one day. The most telling thing, perhaps, is that I don't waste any time worrying about it. As I once so kindly tried to reassure my panda: everything's going to be all right.