ONE in ten new mums suffer from post-natal depression, but because of the stigma surrounding the condition, many decline to seek help and continue to suffer in silence. If, that is, your idea of silence involves a lot of sobbing and yelling.

The mildest and most common form, euphemistically called the "baby blues", is characterised by a tendency to burst into tears for seemingly trivial reasons. Someone (naming no names) puts his red T-shirt in the wash with your pristine white M&S pants and you suddenly find yourself weeping on the kitchen floor clutching a pair of pink frillies and cursing like a trawlerman.

This and other symptoms such as sleeplessness, reduced appetite and feelings of guilt from the milder end of the post-natal depression spectrum are usually relatively easy to treat with counselling or drugs. The problem is that many women feel unable to ask for help.

They feel embarrassed, guilty and ashamed to admit that motherhood, something that we women are supposed to take to like the proverbial duck, has in fact left us fighting for breath as we drown in a murky whirlpool of hormones.

If it sounds like I know what I'm talking about for a change, it's because I was depressed for a year after my son made his grand but somewhat undignified entrance at York District Hospital. His first Christmas, Easter, summer and birthday should have been incredible events in an exhausting but exciting year. Instead they were all overshadowed by the black storm cloud that hovered above me and made every day - even important, landmark days - a struggle.

It was only when my family was on the brink of spontaneous combustion that I finally made an appointment with my doctor. With her help I felt better within a matter of weeks and verging on "normal" - although my family might beg to differ on that point - in just two months.

Luckily mine was a relatively mild if unnecessarily prolonged bout of post-natal depression. Other women, and their families, are not so lucky.

The most severe form of the condition, known as puerperal or post-partum psychosis, affects one new mum in every 500. It usually emerges a few weeks after the birth and begins with restlessness and insomnia. Soon, however, it can result in delusions, hallucinations, manic behaviour and extreme mood swings.

In extreme cases it can also lead to suicide and, unthinkable but not unheard of, the death of a child at the hands of its own mother.

As shocking and deeply disturbing as such a crime might be, in reality filicide - the clinical term for child-killing by parents - is not as rare as you might think.

Dr Phillip Resnick, an American forensic psychiatrist who has examined and interviewed hundreds of women who have killed their children, says those who were suffering from extreme depression or psychosis often had altruistic intent. In other words, they thought their children would be better off dead.

Andrea Yates claims this is why she took her five children and methodically drowned them one after the other in the bath at her home in the middle-class suburb of Clear Lake in Houston, Texas.

She pleaded not guilty to murder by reason of insanity, claiming she was in the throes of post-partum psychosis and was suicidal and suffering from delusions.

Her family confirmed that she had been depressed since the birth of her fourth child two years ago and that she had tried to kill herself with a drug overdose.

The court was also given details of the medication and the psychiatric treatment she had undergone.

Her defence did not convince everyone, however, least of all the jury of eight women and four men, who found her guilty last week.

Andrea Yates might wish she were dead, but that does not mean she deserves the death penalty - the sentence now being considered by the judge. It would be easier for us if she did not exist and we did not have to think about what we humans are capable of. But killing her will not bring back Mary, Luke, Paul, John and Noah, and it will not lessen the pain for her husband, Russell, who has stood by his wife throughout and fervently believes she was - and still is - suffering from extreme post-natal depression.

His life has been destroyed. He has lost all five of his children. This man does not need to have to deal with another death.

Updated: 08:58 Tuesday, March 19, 2002