What causes PMS?
PMS is caused by how your brain responds to the normal rise and fall of estrogen and progesterone after ovulation. People with PMS usually have normal hormone levels, but seem more sensitive to the changes, which affect brain chemicals like serotonin and GABA. That's why PMS appears in the luteal phase and fades a few days after your period starts.
It's sensitivity, not bad hormones
For a long time, people assumed PMS meant hormones were off. Research says otherwise. A key study at the US National Institutes of Health switched off women's cycles with medication: symptoms disappeared in women with PMS. When the researchers added back normal levels of estrogen or progesterone, symptoms returned only in the women who had PMS. The women without PMS got the same hormones and felt fine.
So the cause isn't too much or too little hormone. It's that some people's brains react more strongly to the normal changes. Why that sensitivity exists is still being studied, but genetics seem to play a part.
What happens in the brain
| System | What it does in PMS |
|---|---|
| Serotonin | Helps steady mood, appetite and sleep; falling hormones seem to affect it, which may explain low mood, irritability and cravings |
| GABA and allopregnanolone | A calming brain chemical made from progesterone; its rise and fall may trigger anxiety and tension in sensitive people |
| Prostaglandins | Add physical symptoms like cramps, headaches and loose stools near the period |
| Fluid and salt balance | Hormone shifts can make the body hold water, causing bloating and breast tenderness |
This is also why SSRIs, medicines that work on serotonin, can ease severe PMS within days rather than weeks, and why stopping ovulation stops PMS for many people.
When it happens
What can make PMS worse
- Stress and poor sleep, which make the brain more reactive
- Alcohol and lots of caffeine, for some people
- Low physical activity
- Smoking
- A history of depression or anxiety, which often overlaps with PMS
- Perimenopause, when hormone swings get bigger and less predictable
These don't cause PMS on their own, but they turn the volume up. Read what PMS is or the PMS symptoms list for the full picture, and PMS mood swings for the emotional side.
Because PMS follows your luteal phase, it's predictable. Rating how you feel each day for two cycles shows when your harder days usually start, which is what doctors use to confirm PMS.
See a doctor if PMS affects work, relationships or daily life, if symptoms don't lift after your period, or if you feel hopeless or out of control. That may be PMDD or another condition, and treatment helps. If you ever have thoughts of harming yourself, call your local emergency number, or in the US call or text 988.
Frequently asked questions
Is PMS caused by low progesterone?
Not usually. People with PMS typically have normal progesterone. It's the sensitivity to normal changes that matters.
Is PMS genetic?
It seems to run in families, and twin studies suggest genes play a part in sensitivity to hormone changes.
Why does PMS go away when my period starts?
Once hormones reach their low point and a new cycle begins, the changes that trigger symptoms stop, so symptoms ease within a few days.
Can diet cause PMS?
Diet doesn't cause it, but regular meals, less alcohol and caffeine, and enough calcium may ease symptoms for some people.
Sources
- Schmidt PJ et al. Differential behavioral effects of gonadal steroids in women with and in those without premenstrual syndrome. NEJM (1998)
- ACOG: Premenstrual Syndrome (PMS) FAQ
- Office on Women's Health: Premenstrual syndrome (PMS)
- NHS: PMS (premenstrual syndrome)
This page is for information only and isn鈥檛 medical advice. If something worries you, please talk to a doctor.
Keep reading
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Luteal phase: why feelings get louderWhat the luteal phase is, how long it lasts, why progesterone rises and falls, and the common symptoms: PMS, cravings, low energy and mood changes.
PMS test: do my symptoms follow my cycle?Free PMS test: rate 11 common premenstrual symptoms and see whether yours look like mild PMS, typical PMS or something worth raising with a doctor.