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“Time Of The Month” Can Make A Woman Twice As Likely To Cheat

Mood swings linked to a woman’s hormones may be a source of cheap jokes, but the fact is hormones do have a very powerful effect on how a woman behaves throughout the month.

Just this week a study found that women eat almost 500 calories extra a day in the run up to their periods.

It’s thought this is due to a change in hormone levels which has the effect of making sweet foods and carbohydrates more appealing.

‘Hormones and behaviour are clearly tied into defined phases of the menstrual cycle,’ explains Dr Nick Neave, an associate professor of psychology and behavioural endocrinology at Northumbria University.

As levels fluctuate at different stages of the cycle, mental tasks can become more or less challenging, for instance.

Scientists recently revealed that women become smarter just before their period, due to part of the brain growing.

‘Many women are more rational and controlled after ovulation,’ says Karen Pine, a professor of psychology at the University of Hertfordshire.

‘But they then experience a rise in impulsive behaviour, anxiety and irritability during the next phase, when they are pre-menstrual.’

Here, leading experts reveal the latest thinking about how different times in a woman’s cycle can affect her body and behaviour…



Day one of a woman’s period is the first day of the cycle.

This is the start of the follicular phase, during which time follicles form on the ovary, one of which will mature into an egg, and lasts for about ten to 14 days until ovulation (when an egg is released, ready for conception).

During the follicular phase, the hormone oestradiol (a type of oestrogen) begins to rise, explains Dr Neave.

Oestrogen is important for preparing the egg for ovulation.

But it’s also linked to positive moods, motivation, memory, reduced anxiety and may also help contain stress levels, helping to keep moods stable. 

Rising levels of oestrogen also help to increase libido, which peaks around ovulation.

As a result, this first part of the cycle is the time of the month when most women are at their happiest, adds Dr Virginia Beckett, a spokesperson for the Royal College of Obstetricians and Gynaecologists, who is based in Bradford.

Several studies have shown that women feel more attractive as they approach ovulation — perhaps because it’s nature’s way of encouraging women to have sex during their most fertile time.

Meanwhile their voices rise in pitch (to make them sound more feminine, research suggests), their body odour becomes more sexually attractive (to attract a mate) and they may wear less clothing.

‘Body temperature goes up slightly — because metabolic rate increases slightly — so women may not need to wear as many clothes,’ explains Dr Beckett.

In fact, many ovulation tests use body temperature as a gauge of where a woman is in her cycle.

In an infamous study from 2007, professional exotic dancers were asked to keep a record of their nightly tip earnings for two months.

The women also reported when their periods began and ended, so researchers could calculate when they were most fertile.

Dancers received about £42 per hour when they were near ovulation, but only £33 at less fertile times of the month and £23 while menstruating.



After the follicular phase comes ovulation — the single moment when the egg is released from the ovary.

After this, it only lives for 24 hours — however, sperm can live up to for three days, so if there’s sperm around and an egg floats by, it’s still possible to conceive even if the woman hasn’t had sex on the day of ovulation.

Women are at peak fertility around ovulation, and this is the time they are more likely to adapt their dress style to impress men, says Professor Pine. ‘It’s known as the ornamentation effect.’

This is because females are biologically programmed at this time to prove they are ‘more desirable than the rest of the pack’.

Indeed, a study published in the Journal of Consumer Psychology in 2010 found women are more likely during ovulation to buy clothes, make-up, and other items to boost their attractiveness.

‘Buying a status item is a clear indicator we are at our peak of fertility,’ says Professor Pine, explaining why women are more likely to splash out on something like an expensive bag or pair of shoes at this time.

Women are also twice as likely to engage in extra-marital behaviour around the time of ovulation, adds Professor Pine.

Scientists at the University of Aberdeen and the University of St Andrews found that when progesterone levels are raised during the second half of the menstrual cycle (when the body is preparing for pregnancy) women become more committed to their romantic partners.

But when progesterone is low — in the first part of the cycle before ovulation — women are drawn to masculinity and more likely to have an affair.

Not only that, women may also have better brain function when they are at their most fertile.


Last month, researchers from the Max Planck Institute for Human Cognitive and Brain Sciences in Germany revealed that the hippocampus — the brain area where memories are first formed and which has a key role in emotions — ‘grows’ as oestrogen levels rise.

But as oestrogen levels drop following ovulation as her body prepares for menstruation, this area of a woman’s brain shrinks, MRI scans revealed.

The growth in size and later shrinkage happen ‘with astonishing regularity’ the researchers wrote in the journal Nature Scientific Reports, but more research is needed to establish why.

The stage of a women’s menstrual cycle can even affect how likely a woman is to become addicted to prescription medication such as opioid painkillers.

Scientists at Davidson College, North Carolina found that levels of addictive cravings fluctuated throughout a woman’s cycle.

Their study found that rats were less likely to take addictive substances around ovulation, when their oestrogen levels were high and progesterone levels were about to soar.

Researchers now hope that studying the menstrual cycle could increase a woman’s chances of beating addiction.



After ovulation, a woman enters the second stage of her cycle, called the luteal phase.

This lasts, on average, between 11 and 13 days, until her period starts, and is widely considered a more emotionally difficult time.

The main reason is the empty follicle that once contained the egg triggers the release of another hormone, progesterone, says Dr Neave.

This helps to thicken the lining of the uterus and prepare it in case an embryo is implanted.

But this burst of progesterone is associated with negative mood, which is why, coupled with a decline in oestrogen, so many women feel low in the second part of their cycle, particularly by the end of it when pre-menstrual tension often strikes.

When progesterone is high, in the second half of the cycle, the two sides of the brain become ‘decoupled’, says Dr Neave.

This results in confusion, mood swings, problems finding words and a lack of sharpness.

‘Women also seem to be affected by a lack of oestrogen at this stage, too,’ he says.

‘Part of the brain involved with higher cognitive ability, the prefrontal cortex, responsible for organisation, planning and memory processing, suffers.’

As a result, a woman may walk into a room and forget what she went there for, he adds.

Research by Professor Pine found that women are significantly less controlled and more impulsive with money in the ten days before their periods begin.

‘The later women were in their menstrual cycle, the more likely they were to have overspent,’ she says.

This could be because a shopping spree helps deal with the intense emotions of pre-menstrual tension.


‘Women feeling very stressed or depressed are more likely to go shopping to cheer themselves up – and it’s more socially acceptable than turning to drink or drugs.’

Others, however, turn to carbs.

A paper published in Annales d’Endocrinologie last month found young women significantly increased their caloric intake – of carbohydrates particularly – during ovulation and the luteal phase, eating 500 more calories a day on average.

Sugar, chocolate or carb cravings may also occur ‘because the body is preparing for the fact the woman could be pregnant and wants to lay some fat down’, says Dr Beckett.

And one theory is that eating carbs stimulates production of the ‘feel-good’ brain chemical serotonin.

But try to resist the biscuit tin. ‘Sugary snacks and drinks raise your levels of insulin, disrupting your blood sugar,’ says Dr Beckett.

‘You want to keep your blood sugar stable to help your mood.’



Nearly all women of childbearing age have some premenstrual symptoms in the run up to their period, but women in their late 20s to early 40s are most likely to experience PMT — or report it, at least.

Women on the Pill are far less likely to suffer because the drug supplies a constant dose of hormones, helping balance out any fluctuations.

‘Interestingly, the degree of PMT a woman suffers from isn’t linked to the level of progesterone in her system,’ says Dr Neave.

‘It seems to be about how some women’s brains react to the hormone. Some appear to be hyper-responsive to progesterone.’

How PMT affects women can vary widely. says Dr Beckett.

‘Some women may have a busy job, for example, and not notice their symptoms so much.

‘Others may be more sensitive to hormonal changes, especially just before their period.’

The symptoms vary widely, too.

‘Some women may suffer from constipation,’ says Dr Beckett.

‘This is because progesterone (which is released in this second half of the cycle after ovulation) is a muscle relaxant so can stop waste moving along as it should.’

Along with feeling down, another potential symptoms is water retention — ‘because progesterone can affect the kidneys in a subtle way and the process of clearing fluid from the body slows down,’ she says.

‘You might feel more ‘puffy’, perhaps around the face, and rings feel tighter.’

Eating a poor diet, drinking lots of alcohol, and skimping on sleep can all disrupt the body’s hormone levels, making premenstrual symptoms much harder to deal with.

By the end of the cycle, just before a woman is due to begin her period, all hormones are at a very low level, again potentially lowering her mood.



If there is no fertilised egg implanted in the uterus, levels of oestrogen, testosterone, and progesterone drop, causing the womb lining to break down leading to a period.

Around three out of four women experience period pain. During a period, the muscular wall of the womb starts to contract more to make the lining shed away.

This contraction compresses the blood vessels lining the womb, cutting off the blood supply temporarily and causing tissues in the womb to release chemicals which trigger pain.

The body simultaneously produces prostaglandins, hormone-like compounds that encourage the womb muscles to contract even more – increasing the pain.

When it comes to treating period pain, ibuprofen is more effective than paracetamol.

This was the conclusion of the latest Cochrane Gynaecology and Fertility Group report, compiled by the gold-standard body of independent scientists.

Ibuprofen is a type of drug known as a NSAID (non-steroidal anti-inflammatories) which work against prostaglandins – the hormones responsible for pain.

Peter Bowen-Simpkins, of the Royal College of Obstetricians and Gynaecologists, suggests the best time to take ibuprofen is the day before the period is due, to stop the prostaglandins taking hold.

Other published research suggests NSAIDs can also help reduce menstrual flow.

Some women don’t just have period pains – they also develop migraines.

Scientists have long suspected that fluctuating oestrogen levels may be linked to migraines, and research published earlier this year found women who suffer from regular migraines are likely to have more painful periods.

Experts at Montefiore Medical Centre in New York believe women with a history of migraine experience a rapid oestrogen drop in the days before menstruation.

This ‘two-hit’ system then increases the chance of them suffering more migraines during their periods, along with the lack of sleep, nausea and dizziness that often come during an attack.

But it’s not just pain — menstrual pain and cramps may be associated with brain changes.

Scientists from Taiwan who studied a group of women affected by pain and cramps found evidence of dramatic reshaping, with some brain areas shrinking and others increasing in size — potentially permanently, they reported in the journal Neurology.

The ‘substantial reorganization’ may also have emotional effects, contributing to anxiety and stress at the time and possibly longer term.


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