RETAIL therapy may long have sounded like a convenient excuse for a massive spending spree, but psychologists at the University of Hertfordshire have now discovered biological evidence for why it happens. A study of hundreds of women found impulse buys an

RETAIL therapy may long have sounded like a convenient excuse for a massive spending spree, but psychologists at the University of Hertfordshire have now discovered biological evidence for why it happens.

A study of hundreds of women found impulse buys and extravagant spending sprees were most common in women who were in late stages of their menstrual cycle.

Analysis of 443 women aged 18-50 found those in the last 10 days of their period, known as the luteal phase, had much less control over their spending habits and spent a lot more money on impulse for things they would not need.

Professor Karen Pine, a development psychologist at the Hatfield-based university who led the research, said: "This is a key risk time women should watch out for."

The study found the 153 women in the latter stages of their menstrual cycle had little control over their spending habits.

Two thirds of them admitted to having bought something on impulse, while 57 per cent said they had spent more than �25 than they intended to and six per cent admitted to having spent more than �250 than intended.

The National Association for Premenstrual Syndrome found 90 per cent of women experience some symptoms of premenstrual tension.

Prof Pine, who has published a book on women's relationship with money called Sheconomics, said: "One of the consequences of this is women do get into debt.

"They should be aware of the relationship between their menstrual cycle and their spending and plan their spending habits accordingly.

"Monthly hormonal changes can drive women towards impulsive behaviour, motivated by anger, depression and stress."

Prof Pine added: "Not all women are affected, but those that are should take measures against it.

"Women who are on the Pill are excluded from the effects on spending caused by the menstrual cycle."

Her findings were presented to the British Psychological Society in Brighton last Thursday.

Jason Hurley, director of the debt management advice service Debtmuncher, in Raven Court, Hatfield, said: "Hatfield along with St Albans has one of the largest income to debt ratios in the UK.

"I deal with eight or nine people each day, and they come to me with serious debt problems, which can be up to �400,000 they cannot pay because they have lost their job.

"People can run up to �50-60,000 on their credit cards alone, just by shopping.

"If people are worried about their debt issues, they should look at all their outgoings and bank statements and talk to an independent advisor."

Debtmuncher provides a free, impartial debt advice helpline. Call 01727 758470.