by Dr Jennifer Kelly
Pre-menstrual syndrome (PMS) is a group of both physical and psychological symptoms that can occur towards the end of each monthly menstrual cycle. Typically, the symptoms peak for a few days before your period, and start to improve at the onset of menstruation.1
PMS is thought to affect up to 95% of women in some way, and for most women is considered to be a part of the normal menstrual cycle.2 In most cases, the symptoms may be frustrating, but manageable. However, for 5% of women, the symptoms can greatly affect their everyday lives.3 It is thought that up to 13% of women have taken time off work due to PMS at some stage in their lives, so it has a significant impact on the economy as well.4
We don’t know exactly what causes PMS, but we know that for it to occur the ovaries need to be working normally and releasing hormones. For this reason, PMS does not occur in girls before puberty or in women when they are pregnant, or after the menopause. It is most likely that PMS is caused by a combination of different factors, from hormonal changes during the menstrual cycle, to genetic and environmental factors. PMS is more common after childbirth and in women over the age of 30. We are not sure why, but it is also more common in women who do less exercise or are overweight.5
Women may suffer from physical symptoms such as tiredness, bloating, breast pain, and weight gain, as well as psychological symptoms such as anxiety, sadness, and irritability, or even depression. Physical symptoms can, in turn, also affect mood. For example, tiredness and breast pain can very understandably leave a woman feeling more irritable or low in mood.
The normal menstrual cycle
The average length for a menstrual cycle is around 28 days. However, it is completely normal for women to have cycles of slightly different lengths, and cycles are generally anything from 22 to 35 days long. Day one of the cycle is the first day of your period where the lining of the uterus (womb) starts to break down. At this point, the pituitary gland in the brain is already working to release a hormone called FSH (follicle stimulating hormone), which tells the ovaries to start to mature new follicles (immature eggs).6
It is these follicles that then secrete oestrogen, which in turn results in the release of another hormone called luteinising hormone (LH) around day 13. It is this hormone surge that results in ovulation (the follicle ruptures, releasing the egg). After ovulation, the remainder of the ruptured follicle (the corpus luteum) starts to release another hormone called progesterone. It is soon after this point that some women start to notice some PMS symptoms. For others, it is closer to their period that it starts, although we don’t know why it starts at different points in the cycle for different women.
Increased amounts of progesterone and oestrogen are then released to help thicken up the lining of the womb. It fills with fluids and nutrients to prepare its lining in case you were to become pregnant. If the egg is not fertilised, oestrogen and progesterone levels then drop, and the lining of the uterus starts to break down, forming your period.7
What causes certain PMS symptoms?
In short, the hormones produced by a woman’s ovaries and menstrual cycle are thought to alter various parts of the woman’s body and also her mind, resulting in PMS symptoms. In reality however, it is probably a more complex interaction rather than just changes in hormones.
Premenstrual breast swelling and tenderness, for example, is very common among women, and is thought to be due to increased levels of oestrogen and progesterone in the second half of the menstrual cycle. These hormones are responsible for causing breast glands and ducts to swell at the same time the lining of the uterus is thickened. This swelling results in the slightly swollen, tender breast that may occur before your period. However, water retention is also a problem before a period, and this is likely to increase the problems of breast swelling and tenderness as well.
Premenstrual water retention can cause a bloated, heavy feeling the week or two before your period begins. Some women suffer from this quite badly and can gain over a kilo in body weight due to their period, and then lose it again once their period has started. In most women, the weight gain people describe in PMS is entirely due to this water retention. The exact cause for this unknown, but it is thought that changing levels of oestrogen and progesterone, and another hormone called ADH, may be having an effect. Other sources suggest that a poor diet and high salt intake may exacerbate water retention but there is little robust evidence to back this up.
Stress, irritability, increased crying, and low mood (feeling depressed) are common symptoms described by women in the build up to their period. Again, the exact reason for this is not known, however, it is thought to be partly due to rising oestrogen levels after ovulation, along with other hormonal changes. These hormones are then thought to possibly interact with other brain chemicals. Although it has not been proven, one theory is that the increasing oestrogen levels can result in a drop in serotonin levels in the brain, a chemical that is beneficial to mood and general wellbeing.
In a similar way, increased joint pain and/or a change in bowel habit (diarrhoea or constipation) are thought to be due to changing levels of hormones (oestrogen and progesterone in particular) affecting chemical pathways in the brain. Why this is exactly we are unsure, but water retention is likely to impact on constipation and other symptoms as well. The joint pain may result due to the woman’s body responding to pain chemicals differently during this time period, but again we do not know why.
What other conditions could my symptoms be due to if I don’t have PMS?
There are a number of other conditions that produce similar symptoms to PMS, but usually these conditions do not fluctuate during your menstrual cycle as much. As such, symptoms that you experience constantly are not likely to be due to PMS.
If your symptoms are constant, your GP may wish to rule out conditions such as anaemia, an underactive thyroid, or diabetes if you are tired or low, or depression if your mood is feeling low or depressed. PMS can also produce symptoms similar to irritable bowel syndrome or other bowel conditions, so these may need ruling out. However, some people with IBS do find that their condition flares up around the times of their period. Contact your GP to look into your symptoms if they are new, or you are concerned.
Ways of reducing the symptoms of PMS
Most women with mild PMS symptom benefit from changes to their lifestyle. Simple measures such as regular exercise, regular frequent small balanced meals, stopping smoking, and cutting down on alcohol can make a real difference. However, for some women, if the symptoms are more severe, there are some other options that can help alongside lifestyle changes. These options can include simple painkillers, for example if breast pain is a problem, or trying cognitive behavioural therapy (a psychological therapy) if the symptoms are those of anxiety or depression.
Some women find that using a combined oral contraceptive pill (COCP), particularly if they need contraception too, can really improve their symptoms. It is thought that the COCP can help by regulating hormone surges. As a result, women do not ovulate on the pill and therefore do not get the symptoms. The COCP is not suitable for all women however, so this needs to be discussed with a doctor.8
For those with marked PMS symptoms that are impacting on their quality of life, taking an SSRI (selective serotonin reuptake inhibitor) may be helpful. This is usually a type of treatment for depression, but it can be very useful for severe PMS symptoms as well. Again, this needs to be discussed in detail with a doctor to see if it could be an option for you.9
If you feel your mood is low and you are getting down and depressed, make sure you see your doctor as soon as possible or tell someone you know that can help support you.