I sometimes wonder whether depression originates in nature or nurture. These thoughts tend to happen more during low moments- lucidity of thought coupled with utter absence of ability to actually achieve anything combine into forcing the mood somewhat downwards. Even more so at times like these; in the midst of this eighteen month winter I feel like a small insect that has been pinned to a particularly soggy bit of a collection by some giant entomologist.

My father has a theory that happy people have entirely missed the plot, that they are idiots who are only happy because they have seminally failed to appreciate how ultimately pointless everything is- oh the irony of the self-centred depressive! Irony that was never lost on me even at the age of 9. My theory is that if I had not been brought up by my father I would not be the depressive I have been since early childhood.

I had ten wonderful depression-free years beginning at the birth of Sim, but have been stuck back in the up and down cycle since we got back from Montreal. I don't medicate, I just spiral down into inaction and terminal indecision until I reach rock-bottom and start to head up again.

My mother's way of dealing with shit happening was to collapse into weak laughter and vow one day to write a book about it. I could never understand the laughter but felt that it was no more a rational way of dealing with disaster than getting religion would have been.

Our landlady in Montreal had a theory that depression runs in families as some kind of genetic legacy. Whilst this may be partly true, I've always felt that it is in fact passed on to babies by depressed and unresponsive parenting very early in their life. Dill's wonderful teacher at her last school once asked me if she was like I was as a child. I had to answer truthfully: that she was very much as I would have been had I been allowed to be myself.

When I look at our three, I see few of the signs of depression in them. I worry about them- about how overly laid-back Sim is, sometimes to the point of passivity; about Hen's exceedingly high standards, which thankfully she has so far been able to meet; about Dill's emotional lability, in which she can be laughing one minute and crying the next. They all however seem tough- adversity seems to slide off them in a way it never did with me as a child. I worried about everything, felt guilty about everything. Even now, if someone is a bit "off" with me, my first thought is "what have I said or done to upset them?"

I think the solution is that they do not feel powerless. Powerless as I am to find for myself a direction in which to head out of the black maze when I get stuck in it, I am full of sensible solutions to their everyday problems, can talk them through problems and come up with creative solutions. I am far from a perfect mother but I think I do an OK job. I hope that they will feel empowered in their lives, to be able to change their environment to suit themselves, or failing that, to accept compromise in good grace.

At the same time I also go off at the deep end at them, have entire weeks when everything they do annoys me, when worry about them leads me to say unfair things. I hope and believe that I am equally horrid to all of them when this happens, rather than using my parental model of singling out child of the week for nagging and recriminations.

Dill is just 11 and started senior school last week and is busy joining orchestras and bands at her new school. Sim at 15 is in his last year of compulsory schooling, is preparing for exams, thinking about what he will do next year, and planning his gap in three years' time. Hen at 13 is, to quote from her school report, "a bundle of intellectual and physical energy". I feel so blessed to have them as my children. I just know I don't deserve them.