# Why your mood shifts across the cycle

> Hormones, brain chemistry and why you are not "crazy" for feeling different some weeks.

Category: Mind & mood · 4 min read · Written by the Splash team · Sources checked October 2026
URL: https://splash.care/learn/mind-mood/why-mood-shifts

## Quick answer

- Hormones rise and fall in a monthly rhythm, and your brain may notice.
- Some people are more sensitive to normal hormone shifts, and some have no mood pattern at all.
- Tracking reveals your personal pattern.
- Severe or persistent mood changes deserve medical support.

Ever feel unstoppable one week and like a soggy biscuit the next? Your cycle is a monthly [hormone](https://splash.care/learn/cycle-basics/hormones-explained) rhythm, and those hormones talk to your brain. Mood changes across the cycle are common, and understanding them can make them feel a lot less personal.

## The hormone tide

[Oestrogen](https://splash.care/learn/glossary/oestrogen) rises in the first half of your cycle and peaks around [ovulation](https://splash.care/learn/glossary/ovulation). After [ovulation](https://splash.care/learn/phases/ovulation), [progesterone](https://splash.care/learn/glossary/progesterone) takes the lead, then both fall before your period. Researchers think some people's brains are more sensitive to these normal shifts, and one idea involves brain chemicals like [Serotonin](https://splash.care/learn/glossary/serotonin). The NHS says it is not fully understood why [PMS](https://splash.care/learn/glossary/pms) happens, but it may be down to hormone changes.

- **Period:** Hormones are at their lowest. Some people feel relief as PMS lifts. Others feel tired and inward, especially if cramps are bad.
- **Follicular:** Some people notice more energy and motivation as oestrogen rises. Others notice nothing.
- **Ovulation:** Some people feel social and confident around now. Plenty do not.
- **Luteal:** The second half can bring irritability, anxiety, low mood or tearfulness for people who get PMS.

These are possible patterns, not rules. Not everyone has a mood pattern at all. When researchers followed people day by day, about 4 in 10 studies found no link between mood and cycle phase in people who were not seeking help for [PMS](https://splash.care/learn/conditions/pms). But for a good number of people, and for the minority with [PMDD](https://splash.care/learn/glossary/pmdd), the pattern is real and sometimes severe. Your rhythm is yours, which is exactly why [tracking](https://splash.care/learn/cycle-basics/tracking-101) is so useful.

**Myth:** Mood changes before your period are "all in your head".

**Fact:** PMS is a recognised health condition. The NHS lists mood swings, feeling depressed or irritable, and feeling anxious or emotional among its symptoms. They are physical as well as emotional.

**Myth:** Everyone gets moody before their period.

**Fact:** Not so. The NHS says most people have PMS at some point, but symptoms differ from person to person and month to month. A review of day-by-day studies found no consistent mood pattern in many people. Having no pattern is just as normal.

> **Splash says:** log your mood daily for a couple of cycles. When you see that wobbly Tuesday lands on cycle day 24 every month, it suddenly feels a lot more manageable. No pattern? That is useful to know too.

**Quick quiz:** What does research following people day by day tell us about cycles and mood?

1. Everyone has the same mood pattern
2. Patterns vary a lot, and many people have none
3. Hormones have no effect on anyone's mood

Answer: Patterns vary a lot, and many people have none. Many studies found no clear link in people not seeking help for PMS, while a minority have strong premenstrual symptoms. Your own log tells you which group you are in.

### When to see a doctor

If mood changes are severe, last most of the month, or affect work, school and relationships, talk to a GP. Severe cyclical mood symptoms may be PMDD, which is treatable. If you ever feel unsafe or have thoughts of harming yourself, please reach out now. If you are in danger, call 999 or go to A&E. For urgent help that is not an emergency, call NHS 111 and choose the mental health option (England), or call Samaritans free on 116 123, any time. You can also text SHOUT to 85258.

## Sources

1. [NHS: PMS (premenstrual syndrome)](https://www.nhs.uk/conditions/pre-menstrual-syndrome/)
2. [Romans et al. (2012) Mood and the menstrual cycle: a review of prospective data studies, Gender Medicine](https://pubmed.ncbi.nlm.nih.gov/23036262/)
3. [Robinson et al. (2025) Nutritional interventions and the psychological symptoms of PMS: systematic review, Nutrition Reviews (background on PMS and PMDD)](https://pmc.ncbi.nlm.nih.gov/articles/PMC11723155/)
4. [Jean Hailes: Premenstrual syndrome (PMS)](https://www.jeanhailes.org.au/health-topics/periods/premenstrual-syndrome-pms/)

This is general information, not medical advice. Splash can’t diagnose. If you’re worried, talk to a GP, pharmacist or sexual health clinic. In an emergency call 999 (UK) or 911 (US).