What Is PMS? Symptoms, Causes and What May Help

In brief:

• Symptoms start after ovulation and ease within a few days after your period begins.
• The exact cause is unknown; sensitivity to changing hormones throughout the cycle is thought to play a role.
• Regular exercise, nutrition, sleep and stress management are the first steps.
• If symptoms interfere with daily life or are very severe (PMDD), see a doctor.

What is PMS?

Premenstrual syndrome is a group of symptoms that start in the second half of the cycle, after ovulation, and ease with menstruation (US Office on Women's Health). A similar onset in each cycle and resolution after the period are the main features distinguishing PMS from other conditions.

PMS is very common. According to the US Office on Women's Health, more than 90% of women report some premenstrual symptoms, and up to three in four say they have experienced PMS symptoms at some point. It is most common in the thirties; symptoms may increase in the late thirties and forties as menopause approaches.

When does PMS start?

PMS symptoms usually start one to two weeks before a period and disappear within a few days after it begins. Doctors look for this pattern when considering PMS (US Office on Women's Health):

• Symptoms occur in the 5 days before a period,
• This repeats for at least three cycles in a row,
• Symptoms go away within 4 days after the period starts,
• Symptoms affect daily life.

What are the symptoms of PMS?

Symptoms can vary from month to month (NHS). The most common are:

Emotional symptoms:

• Mood swings
• Irritability, tension
• Anxiety, feeling more emotional
• Unhappiness, low mood

Physical symptoms:

• Bloating or cramps
• Breast tenderness
• Headache
• Acne, greasy hair
• Tiredness, changes in sleep patterns
• Appetite changes, food cravings

We explain the reasons for premenstrual sweet cravings and mood changes in Sweet Cravings and Mood Changes During PMS.

What causes PMS?

The exact cause is not fully understood (NHS). Changing hormone levels during the cycle, and greater sensitivity to these changes in some women, are the leading explanation. The same hormonal change may cause noticeable symptoms in one woman and go unnoticed in another. Stress, lack of sleep and smoking may make symptoms worse.

PMS or PMDD?

Premenstrual dysphoric disorder (PMDD) is a much more severe form of PMS. The symptoms are similar but much more intense; deep sadness, hopelessness, intense anger or anxiety seriously affect work, school and relationships (NHS). According to the US Office on Women's Health, it affects fewer than 5% of women of reproductive age.

If you suspect PMDD, see a doctor. If you have thoughts of harming yourself, call 112 or go to the nearest emergency department without delay (NHS).

What may help with PMS?

Keep a symptom diary

Record your symptoms and the days they begin for at least two cycles (NHS). This helps you see the pattern and gives you concrete information to discuss with a doctor. Symptoms beginning before a period and easing when it starts suggest PMS.

Regular exercise

Regular aerobic exercise throughout the month, such as walking, swimming or cycling, is recommended (US Office on Women's Health, NHS).

Nutrition

The NHS recommends a balanced diet and small meals every 2–3 hours. The US Office on Women's Health also recommends reducing caffeine, salt and sugar in the two weeks before a period.

Sleep and stress

Try to sleep for about eight hours each night (US Office on Women's Health). Stress reduction methods such as yoga and meditation may help (NHS). Smoking and excessive alcohol may worsen symptoms.

Supplements: what does research say?

According to the US Office on Women's Health summary:

• Calcium: Studies show that it can reduce some PMS symptoms.
• Vitamin B6: It may help with symptoms such as mood swings and bloating.
• Magnesium: Results are mixed; it may help with some symptoms.
• Omega-3 and omega-6 fatty acids: They may help with cramps and some other symptoms.

A meta-analysis combining 14 studies of chasteberry (Vitex agnus-castus) found a significant reduction in symptoms. However, most studies had a high risk of bias and results varied widely; the authors state that no firm conclusion can be drawn (Verkaik et al., 2017). For details, see What Is Chasteberry? What Are Its Benefits for PMS? and Is All Magnesium the Same?.

Consult your pharmacist or doctor before taking supplements, especially if you take regular medication (NHS).

Options a doctor may recommend

If lifestyle changes are not enough, a doctor may consider options such as hormonal methods including the contraceptive pill, cognitive behavioural therapy or certain antidepressants (NHS). These decisions are individual.

When should you see a doctor?

• If symptoms do not improve despite lifestyle changes
• If symptoms significantly affect work, school or relationships
• If symptoms continue after your period
• If you experience deep hopelessness or thoughts of harming yourself (get help without delay)

Frequently asked

How many days before a period does PMS start?

It usually begins one to two weeks before a period, after ovulation. Most symptoms intensify in the last 5 days before a period and go away within 4 days after it starts (US Office on Women's Health).

Does PMS change with age?

It is most common in the thirties and may increase in the late thirties and forties as menopause approaches (US Office on Women's Health). For changes during this stage, see What Is Perimenopause?.

Can PMS and pregnancy symptoms be confused?

Yes, some symptoms can overlap: breast tenderness and tiredness also occur in early pregnancy (NHS). If your period is late and pregnancy is possible, take a test; home tests are most reliable from the first day of a missed period (NHS).