Sex and the City character Carrie Bradshaw loves to shop
Women may be able to blame impulse buys and extravagant shopping on their time of the month, research suggests.
In the 10 days before their periods began women were more likely to go on a spending spree, a study found.
Psychologists believe shopping could be a way for premenstrual women to deal with the negative emotions created by their hormonal changes.
Professor Karen Pine will present her work to a British Psychological Society meeting in Brighton later this week.
She asked 443 women aged 18 to 50 about their spending habits.
Almost two-thirds of the 153 women studied who were in the later stages of their menstrual cycle - known as the luteal phase - admitted they had bought something on an impulse and more than half said they had overspent by more than £25.
A handful of the women said they had overspent by more than £250.
And many felt remorse later.
Professor Pine, of the University of Hertfordshire, said: "Spending was less controlled, more impulsive and more excessive for women in the luteal phase.
"The spending behaviour tends to be a reaction to intense emotions. They are feeling stressed or depressed and are more likely to go shopping to cheer themselves up and using it to regulate their emotions."
She said much of this could be explained by hormonal changes during the menstrual cycle. And the findings were exaggerated in the women with severe PMT.
"We are getting surges and fluctuations in hormones which affect the part of the brain linked to emotions and inhibitory control. So the behaviour we found is not surprising."
Another explanation might be that women are buying items to make themselves feel more attractive - coinciding with the time of ovulation when they are most fertile, typically around 14 days before the start of a period.
Most of the purchases made by the women were for adornment, including jewellery, make-up and high heels.
Professor Pine said: "Other researchers have found there is an ornamental effect around the time of ovulation."
Researchers have found women tend to dress to impress during their fertile days.
Professor Pine, author of the book Sheconomics, said if women were worried about their spending behaviour they might avoid going shopping in the week before their period was due.