Everything is fine.
And then suddenly it absolutely is not.
Your inbox feels like a personal attack. Someone says “no worries” and, for reasons you cannot fully explain, there are suddenly quite a lot of worries. Or perhaps there is no irritation at all. Instead, you feel anxious, unusually sensitive, flat or like crying because you saw an elderly dog waiting outside a bakery.
Then your period arrives.
Ah.
Mood changes are among the symptoms frequently associated with premenstrual syndrome (PMS). But despite generations of jokes about women becoming “hormonal”, the relationship between the menstrual cycle and mood is considerably more nuanced than hormones make women emotional.
So, what does research actually tell us about PMS and mood changes, why might some people be more affected than others and when are emotional symptoms worth discussing with a healthcare professional?
What is PMS?
Premenstrual syndrome, usually shortened to PMS, describes a group of physical, psychological and behavioural symptoms that occur in relation to the menstrual cycle.
Symptoms typically develop during the luteal phase, the part of the menstrual cycle after ovulation and before menstruation. They usually improve after the period begins.[1]
Physical PMS symptoms can include bloating, breast tenderness, headaches, tiredness and changes in appetite.
Emotional and behavioural symptoms can include:
- irritability
- mood swings
- feeling anxious or tense
- feeling sad or low
- increased emotional sensitivity
- difficulty concentrating
- changes in sleep
- changes in appetite or food cravings.[1]
Not everybody experiences PMS, and those who do don't necessarily experience it in the same way.
One person's PMS might be predominantly physical. Another person's most noticeable symptom might be irritability. Someone else might feel more anxious or tearful.
Your menstrual cycle did not receive a standardised operating manual, unfortunately.
Why can your mood change before your period?
The obvious answer would seem to be:
Hormones.
And yes, hormones are involved. But that answer is incomplete.
During a typical menstrual cycle, levels of hormones including oestrogen and progesterone change considerably. After ovulation, progesterone rises and then, if pregnancy does not occur, both progesterone and oestrogen fall as menstruation approaches.
Researchers believe that premenstrual symptoms may be related not simply to the amount of these hormones circulating in the body, but to individual sensitivity to normal hormonal fluctuations.[1]
This is an important distinction.
PMS isn't necessarily a case of having “wrong” hormone levels that simply need to be “balanced”. Two people can experience similar hormonal changes across their cycles and have very different emotional experiences.
The brain's response to those changes appears to matter too.
What does serotonin have to do with PMS?
You may have heard serotonin described as the “happy hormone”. Technically, it is a neurotransmitter rather than a hormone, and its role is much more complicated than simply switching happiness on and off.
Serotonin is involved in processes including mood, sleep and appetite. Researchers have investigated how changes in ovarian hormones may interact with serotonin systems in the brain as one possible explanation for premenstrual mood symptoms.[1]
This relationship is also relevant because selective serotonin reuptake inhibitors (SSRIs), a class of medicines more commonly associated with depression and anxiety, can be used to treat severe premenstrual symptoms.[1]
That does not mean that everybody who gets irritable before their period has a serotonin deficiency.
Bodies rarely give us anything quite that tidy.
Instead, current thinking points towards a complex interaction between normal hormonal fluctuations, brain chemistry, individual sensitivity and other biological and environmental factors.
Is feeling emotional before your period normal?
Some degree of mood change around menstruation is common.
The World Health Organization (WHO) notes that people who menstruate may experience anxiety, sadness or depressed mood, irritability and other mood changes over the course of the menstrual cycle, including before or during menstrual bleeding.[2]
But there is a very important word in that sentence:
May.
Not everyone experiences noticeable mood changes before their period. And menstruating doesn't make someone inherently less rational, less emotionally stable or less capable.
That stereotype has been hanging around for considerably longer than it deserves.
The existence of genuine premenstrual mood symptoms does not justify dismissing someone's feelings with:
“Are you on your period?”
Sometimes your hormones may be influencing how you feel.
Sometimes somebody is simply being annoying.
Both things can be true.
PMS mood swings: what do they actually feel like?
The phrase “mood swings” can make PMS sound almost cartoonish, as though you spend the morning crying and the afternoon throwing plates.
Real experiences can be much subtler.
You might notice that you have less patience than usual. A minor inconvenience feels disproportionately irritating. You might feel more vulnerable to criticism, more anxious about something you would normally handle easily or unusually pessimistic.
Some people describe feeling less resilient during the premenstrual phase. Things that would usually bounce off suddenly seem to stick.
Others notice changes in motivation, concentration or their desire to socialise.
None of these experiences on their own proves that PMS is responsible. The important clue is repetition and timing.
The pattern matters
One bad day before a period isn't enough to establish PMS.
PMS is characterised by symptoms occurring in a cyclical pattern in relation to menstruation. RCOG recommends keeping a symptom diary for at least two menstrual cycles when PMS is suspected.[1]
This can be surprisingly illuminating.
Try noting:
- the first day of your period
- when mood changes begin
- what those changes feel like
- their severity
- when they improve
- sleep and energy levels
- physical symptoms
- whether symptoms interfere with work, relationships or everyday life.
After a couple of months, you may start to see a pattern.
Or you may discover that your colleague really does annoy you every Thursday regardless of where you are in your cycle.
Useful information either way.
PMS or just everyday stress?
This is where menstrual-cycle conversations can become tricky.
Stress, poor sleep, work pressure, relationship difficulties, anxiety, depression and approximately 847 other aspects of being a human can affect mood.
The menstrual cycle doesn't happen inside a laboratory. It happens while you're working, parenting, studying, arguing with customer service, worrying about money and trying to remember whether you bought toilet roll.
So not every emotional change that occurs before menstruation is necessarily caused by PMS.
Existing mental health conditions can also become worse during particular phases of the menstrual cycle. This is sometimes referred to as premenstrual exacerbation.
Tracking symptoms throughout the whole cycle, rather than only paying attention during the days before your period, can help reveal whether symptoms are predominantly premenstrual or present more consistently.
PMS vs PMDD
For some people, premenstrual mood symptoms go well beyond feeling a bit irritable or emotional.
Premenstrual dysphoric disorder (PMDD) is a recognised disorder involving severe cyclical symptoms, particularly psychological and mood-related symptoms, that can substantially interfere with everyday functioning.
These can include severe irritability, depression, anxiety, mood swings and feelings of hopelessness.
PMS and PMDD are related, but they are not interchangeable.
We take a closer look at the differences, diagnostic terminology and typical timing in our guide to PMS vs PMDD: What's the Difference?
If your premenstrual mood changes are severe or regularly affect your ability to work, study, maintain relationships or function normally, don't assume you simply have to put up with them.
When should you talk to a healthcare professional?
The WHO states that menstrual symptoms involving depressed or anxious mood, or other symptoms that disrupt normal activities, are valid reasons to seek healthcare.[2]
Consider speaking to a qualified healthcare professional if your premenstrual mood symptoms:
- significantly interfere with everyday life
- affect work, education or relationships
- feel increasingly difficult to manage
- involve severe anxiety or depression
- happen predictably for a significant part of every month
- make you feel unlike yourself to a degree that concerns you.
You don't need to prove that your symptoms are “bad enough” before mentioning them.
A symptom diary can be particularly useful to take to an appointment because it gives both you and your healthcare professional a clearer picture of what is happening across the menstrual cycle.
If you experience suicidal thoughts, feel at risk of harming yourself or don't feel able to keep yourself safe, seek urgent professional help rather than waiting for your period to arrive.
Can you do anything about PMS-related mood changes?
There isn't one universal PMS management plan because symptoms, severity and individual circumstances vary.
For significant PMS, medical management can include approaches such as cognitive behavioural therapy, certain hormonal treatments and SSRIs.[1]
For milder symptoms, some people find it useful to pay attention to factors such as sleep, regular movement, stress and their general routine.
And then there are the little rituals that don't need to pretend to be medical treatments to earn their place.
Closing the laptop. Putting your phone on silent. Taking a bath. Going for a walk. Cancelling an entirely optional social engagement without writing a 400-word apology.
Or making tea.
Sometimes you just need the kettle
There is something pleasantly uncomplicated about the ritual of making a cup of tea.
Boil water. Choose mug. Steep tea. Sit down for five bloody minutes.
It isn't a treatment for PMS, and we're not going to tell you that a herbal infusion can magically “balance your hormones”, regulate your serotonin or make premenstrual mood changes disappear.
But comfort doesn't need to be a medical claim to have value.
That's very much the thinking behind our Stay Calm and Drink On herbal tea. It's a blend for those moments when everything feels a little much and you fancy turning making a cup of tea into permission to stop for a moment.
No promises of hormonal harmony. No claims that your uterus and brain will suddenly sign a peace treaty.
Just herbs, hot water and a very good excuse to put the rest of the world on mute for a few minutes.
References
[1] Royal College of Obstetricians and Gynaecologists (RCOG). Managing premenstrual syndrome (PMS). Patient information covering PMS symptoms, cyclical timing, possible mechanisms, diagnosis and treatment options.
RCOG: Managing premenstrual syndrome (PMS)
[2] World Health Organization (2026). Menstrual health. WHO overview of menstrual health, including mood changes associated with the menstrual cycle, symptoms that warrant medical attention and current gaps in menstruation research.
WHO: Menstrual health
This article is for general information only and isn't intended to diagnose, treat or replace individual medical advice. If mood changes or other premenstrual symptoms are significantly affecting your wellbeing or everyday life, speak to a qualified healthcare professional.
