You might notice it in small moments. A message feels harder to answer, or an interruption gets under your skin more than usual. Then you realize your period is a few days away and wonder whether the timing has something to do with it.
Your cycle may be part of the explanation. Estrogen and progesterone, two hormones involved in your menstrual cycle, also affect how your brain works. As their levels change, some women notice changes in their mood.
What your hormones are doing before a period
Hormones are chemical messengers that carry signals around your body. Estrogen and progesterone help prepare the lining of your uterus, or womb, for a possible pregnancy.
Ovulation is when an ovary releases an egg. In a cycle with ovulation, these changes happen in sequence:
- Before ovulation, estrogen rises. It helps build up the lining of your uterus.
- After ovulation, progesterone rises. It helps prepare that lining for a possible pregnancy. Estrogen has a second, smaller rise during this part of the cycle, called the luteal phase.
- If pregnancy doesn't happen, both hormones fall toward the end of the cycle. The lining then sheds as your period.
So by the time bleeding begins, your body has already been going through changes for days.
Where your brain comes into the picture
Your brain uses chemical signals to regulate mood and respond to stress. Estrogen influences serotonin, one of the chemicals involved in mood. Progesterone takes a different route: your body turns it into allopregnanolone, which strengthens the effects of GABA, a chemical that helps quiet nerve activity. This system plays a part in how your brain responds to anxiety and stress.
As progesterone rises after ovulation and falls before your period, allopregnanolone levels change too. Researchers studying PMDD, a condition involving severe premenstrual symptoms, think differences in how the brain adjusts to these shifts may leave it more reactive to emotional situations.
That offers one possible explanation for why a small frustration can feel harder to handle at this point in the cycle. Hormone levels can be within the usual range while the brain is particularly sensitive to their changes. Researchers are still studying how far this explanation applies to milder premenstrual mood changes.
Why you might feel more sensitive before your period
The time after ovulation is when premenstrual symptoms can appear. You might have less patience than usual, feel more anxious, or find yourself getting upset more easily. Tiredness or bloating can show up around this time too.
The drop in hormones just before bleeding is one part of the picture. Symptoms can also begin earlier, while progesterone is still rising.
Why you may feel more like yourself when your period starts
Perhaps you've noticed that some of the irritability or tension begins to ease once your period arrives. That's a pattern described in PMS: symptoms often improve around the start of bleeding and over the next few days.
Estrogen and progesterone are still relatively low at the beginning of a period. Feeling better at this point doesn't mean they've suddenly jumped back up.
Researchers recognize this timing, but they're still studying the full explanation for it. Sensitivity to changing hormone levels appears to play a part.
Your next cycle may feel different
You might notice a familiar change before one period and very little before the next. Symptoms can vary between women and from month to month. There isn't one emotional pattern you have to fit.
Your everyday life still matters, too. A difficult conversation or a demanding week at work deserves attention in its own right. Understanding your cycle gives you another way to make sense of how you're feeling.
If you're curious about your own timing, you can log your period days and select the moods that match how you feel in GetMyMood. There's an optional space for a note, too.
When mood changes are getting in the way
If mood changes are making it hard to work, manage everyday tasks or spend time with people you care about, speak with a qualified healthcare professional. You don't have to work out the cause or establish a monthly pattern before asking for support.