POSTNATAL depression is a throwback to the cavewoman era, it has been suggested.

Experts from Edinburgh University have said that the condition, which affects thousands of women in Scotland, including the television presenter Gail Porter, probably evolved as a genetic response to prehistoric conditions.

The illness is a result of fluctuating hormone levels, which are naturally designed to cause an increased level of aggression after the birth of a child, according to Dr Simone Meddle of the university’s Centre for Integrated Physiology.

She said that the behavioural change was designed to help a mother protect her new-born child from predators.

But as human life has become safer the defence mechanism has become redundant, with the effect that many women feel an overwhelming sense of despair and depression.

“There are huge changes in the blood and brain of a mother when she gives birth,” Dr Meddle said. “But while in our evolutionary past these may have been beneficial, now they can have a detrimental effect.”

She believes that the condition is caused by the absence of a powerful chemical produced in the brain called vasopressin, which is forced to lie dormant after a woman has given birth.

Dr Meddle has received £250,000 from the Biotechnology and Biological Sciences Research Council for a three-year study on how the hormone works in rats.

“Female rats are normally docile, but when they have offspring they become extremely defensive,” she said.

“Their aggression levels soar and they attack intruders. Sometimes the aggression causes the mother to turn on her (own young).

“By better understanding what is going on, we will hopefully develop ways of preventing postnatal depression.” Figures from the Scottish Executive show that 11,000 women in Scotland suffer from the condition in a given year.

But some experts say that this figure under-estimates the problem. Bluebell Day, a national awareness campaign, has been organised by the Church of Scotland in a bid to help women to recognise postnatal depression and seek help for it. Money raised by events on June 6 will be spent on research and advertising to raise the profile of the condition.

Gail Porter has had the condition since the birth of her daughter, Honey, who is now two.

Porter, 34, who is a former host of Big Breakfast and Top of the Pops, has said that it was a “nightmare” facing her post- natal depression.

She was prescribed pills, but eventually decided to stop taking them without telling her doctor.

She recently took an overdose, although she has denied that it was a suicide attempt or that she had intentionally taken too many pills.

“I was crying all the time and I thought I’m doing this wrong, and doing that wrong, I’m a terrible mother,” she said.

“I was so tired of trying to make everything perfect. The doctor said it was postnatal depression. I have got a lovely daughter and I wouldn’t want to do that.

“You do not want to tell anybody, you just want to keep it to yourself. But I didn’t realise how many people suffered from it.”

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