There's a time of year that I dread like no other - it's when I have to bring the cats to the vet. So far, it's looking good. I brought out the catbox hours ahead of the appointment, and put it in the centre of the floor. The two of them, big beautiful black siblings, immediately woke up and started nosing around it, examining it from all angles, gingerly stepping in and out for size, aroma, and comfort. As I write, one is settling down for a nap inside, and the other is standing guard outside.

How quickly they forget the trauma that it signifies for them - later on, there will be tears and gnashing and wailing and scratched skin as they are carted off to the nasty man who sticks needles in them. When I take them home they will sulk for days, run from me as if I'm evil incarnate, and it will be psychological warfare at its bloodiest: guilt, revenge, punishment, high-drama sulking. But I am prepared. The trick is to have faith that, in the greater scheme of things, the short-term carnage is worth it, no matter how much of a quivering wreck we all are at the end of the day. But the animals don't know it. That knowledge of seeing ahead is reserved for us humans.

There's a mythological creature that's big these days in New Age mythology and astrology - Chiron, the centaur king, half horse and half human. Wiser than most centaurs, who were generally a rowdy drunken lot, he taught many of the ancient heroes in Greek mythology. He was a healer and philosopher - and his teaching was rich because he couldn't heal himself of a wound that was accidentally inflicted on his animal half by a poisoned arrow gone awry.

However, instead of getting bitter and twisted about it, he gamely persevered and grew in compassion and wisdom. But as he was an immortal, he didn't have the relief of death to look forward to - he was faced with an eternity of coping with that damn pain. So in the end he did a deal with this mortal guy called Prometheus, who was doing time on a daily regime of liver-plucking for his sin of stealing the fire of foresight. They swapped places, and Chiron got the peace he longed for. There were no easy answers in his life, in trying to reconcile the civilised wise part of him and the wounded animal part - perhaps this split is something that describes well the condition we call human at the start of this century.

As much as we crave it, our animal instinctive biological drives and needs are not for taming. Like animals, they cannot be reasoned with - for my cats, a cage is a cage, a needle is a needle, betrayal is betrayal. Increasingly, primitive needs in our culture are being ignored - needs for physical contact, hugging, touching, affection (especially as more and more people are living alone); needs for rest (often we have to get ill with a cold or worse in order to give ourselves the rest we need); and biological drives and needs for sex and breeding.

We are getting slightly more literate about our emotional needs and mental health issues, but not spectacularly so. A recent report says that one in four of us suffers from depression at one stage in our lives. Between 12% and 15% of students at university are depressed, with university counsellors reporting a dramatic rise in severe mental health problems among their charges. I've already written about the increase in suicides in young people, especially young men.

As ever with the mysterious trends that affect our collective, it is difficult to say if the fact that there are "easy" medical treatments available now for depression is an encouragement for people to report it. Whatever the reasons for the headline-grabbing rise, medication alone cannot be the answer - for unless we understand the reasons why we are so out of sync with our "animal" natures we are doomed to stay split. To endure illness, especially the agony of severe depression, without learning from it afterwards, is to make a mockery of that which is our greatest gift - our capacity to make meaning from suffering, to see patterns and symbols, and to find faith in a Bigger Picture, to see the soul in our symptom.

My own depression last year, and the experience of "submitting" to an SSRI anti-depressant in August, has been a hugely educational experience for me. I'm still on the medication and in many ways my life has improved beyond comparison - I'm back to my "old self". Trouble is, I don't think I ever was my "old self" in the first place. Anxiety has always dogged me, to varying degrees, a low-level panic, a hypersensitivity to the world around me. With the safety net of this medication, I feel less anxious, more able to cope with life - and it's totally changed my relationship to my sexuality, which I didn't expect.

Right now, the prospect of living as a monk in a forest cave for a year or two seems highly appealing to me - my interest in rough and ready sex as recreation or escape or as a motor for fantasy has disappeared, replaced with a slow and exquisitely fragile taste for tenderness, with hell to pay if there's anything gauche or clumsy under the duvet. Not easy for my beautiful, bewildered, bothered and differently sensitive beloved. Not easy for me, either - it's as if I'm getting acquainted with a different body, a different biological component to the whole of me. Which of course is what the drug does, it changes biology. Like all drugs. I suppose I'm really recording here my marvel at how subtle and powerful the connection between body and mind is.

Emotions are a trigger to thought - and biology influences feelings far more than I could ever have realised. I, therefore, am discovering myself anew these days - and, to be quite honest, sometimes I don't recognise myself. I used to write from a me-against-the-crazy-world perspective, never going into all-men-are-bastards territory but skirting close sometimes. Somehow, my words here have been fuelled sometimes by a depressive angry angst, no matter how much of a light twist I tried to apply to them. Different things bother me now, different things give me pleasure. How long will it last? Will I return to my old ways once I stop taking the pills? Will I have learned new ways of coping that will triumph over my excessively voracious biology in the future? Fuck knows. It's all an adventure, really. But it's one I'm glad I'm on.

Here, kitty kitty kitty. Into the box, this nice comfy box. It's for your own good... believe

me...