THE DAY the clocks go back can be traumatic. Everyone feels a bit down in the winter - but some of us go further down than others. My GP diagnosed that I was suffering from seasonal affective disorder - SAD - about six years ago, but now I realise that I must have had it for about 12 years.

SAD is almost a kind of human hibernation - our unofficial logo is the hedgehog. Research that's going on at the moment suggests it's to do with melatonin, which is something the brain normally produces at night. SAD sufferers seem to produce much more of it, which has a depressing effect.

I feel at my lowest in January and February. A lot of people start to pick up in March or April time, but I'm much slower - it depends on the weather, but it could be May or June. It begins again early in the autumn - around the end of August, I notice I'm slowing down, starting to catnap during the day, starting to eat more.

The eating more is a carbohydrate craving for starchy, sugary things. A SAD sufferer would kill for a Mars bar] And then of course you gain weight - yo-yo weight gain is a very typical symptom. You get a disturbed sleep pattern as well - because of sleeping during the day, you find that you're not sleeping well at night. You get aching in your joints, especially in your hands and wrists, you get very irritable and short-tempered. It's like having PMT all winter - the symptoms are very much like that. Your social life just cuts off - most SAD sufferers say they hate Christmas, because of the effort involved.

I've got two children, Robert who's 17 now, and Laura who's 14, so I've had SAD for a good portion of their lives. It's the family that bear the brunt - when you're at home with them you let go. When the children were younger they couldn't quite understand that I couldn't help being bad-tempered and shouting at them and wanting to go to bed just as they were coming in from school.

Now I'm used to SAD I've geared myself a bit more to it. You get very anxious and your self-esteem goes down to rock bottom as you struggle to keep the house together, keep the children going, and I work as well. You can get into the most awful state. Now I take a deep breath, step back, let things go.

I've realised how lucky I was that my GP knew what SAD was and believed in it. So many people are told by their GPs to go home and pull themselves together, which is no help at all.

She gave me anti-depressants for a couple of winters until she was sure that her diagnosis was right. We'd talked about finding out more about lightbox treatment, and she referred me to the research unit that runs from the Royal Southampton Hospital. I did some trials for them, and now I have a box at home - it cost about pounds 100. It's a couple of feet across, a foot high, with three strip lights in it which ape natural daylight as closely as possible.

I find it very difficult to get out of bed to use it, so I've got it on a timeswitch, and it comes on at six o'clock in the morning - I've got used to it, but it wakes my husband up. I get about an hour then, and I try to use it again in the evening as the winter gets going. You don't have to stare into it all the time as long as you glance at it fairly frequently. You can read, watch television, while you're using it - I use my knitting machine in front of it.

We have taken holidays in winter, which is lovely, you get a couple of weeks relief, but you have to get cracking with the treatment straight away when you get back, because it only takes two or three days to go down again. My husband says 'Where shall we go to live when I retire?' Florida springs to mind.

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