Why mood swings happen during periods


Premenstrual syndrome (PMS), or period mood swings in women, is a complex condition, a tough nut to crack. It’s mainly because its symptoms are wide-ranging and vary considerably in severity from one woman to another.

PMS occurs in what is known as the luteal phase of the menstrual cycle. It’s a two-week phase between ovulation (release of the egg) and menses (discharge of blood).

PMS is a combination of physical and psychological symptoms that are linked to the hormonal changes that occur during this period, which explains why taking oral contraceptives can abate these symptoms.1

The physical symptoms include tender breasts, bloating, muscle aches, cramps, and headaches. The psychological symptoms include sadness, anger, irritability, trouble concentrating on tasks, and withdrawal from family and friends.

period mood swings

The psychological symptoms of PMS ring a bell

The psychological symptoms of period mood swings can provide a clue to understanding why it happens. For starters, they’re remarkably similar to the symptoms of depression. In fact, depression itself is considered one of the psychological symptoms of period mood swings.

In my book Depression’s Hidden Purpose, I threw light on how depression is best understood as an adaption to solve complex life problems that require a good deal of reflection and planning.

Inability to concentrate and withdrawal from family and friends are prominent symptoms of depression so it’s not unreasonable to think that the same symptoms in period mood swings might function to help a woman solve a complex life problem.

The fact that PMS happens in a very specific phase of the menstrual cycle after ovulation suggests that period mood swings must have something to do with a woman’s reproductive success, or more specifically- the success of conception.

Failed conception and period mood swings

PMS happens when an egg is released but isn’t fertilized by a sperm. The woman doesn’t conceive. Had the woman conceived, there would be no PMS since PMS doesn’t happen during pregnancy when the menstrual cycle ceases temporarily.

Period mood swings could be a signal to the woman that some kind of loss has happened. Our negative emotions mainly evolved to signal to us that something is wrong.

So PMS could be a signal to the woman that something is wrong, and in this case, this ‘something’ is ‘the egg not fertilizing’. It should’ve been fertilized. The inability to focus on tasks and withdrawal from family and friends would then force the woman to re-evaluate her life and current relationship.

PMS only happens in reproductive-age women, that is, child-bearing women between puberty and menopause. It becomes more severe in later years as the woman passes her peak fertility period and approaches menopause.2

The need to conceive and pass on your genes becomes greater than ever during such a period because of the small window of opportunity.

PMS occurs in three out of every four menstruating women. When a trait is that common in a population, it hints at an adaptive value of the trait.

PMS as an adaptation to dissolve infertile pair bonds

Interestingly, researchers have suggested that PMS had a selective advantage because it increased the chance that infertile pair bonds would dissolve, thereby improving the reproductive outcomes of women in such relationships.3

This is in line with the fact that hostile behavior shown during period mood swings is often directed toward one’s relationship partner. Add to this the finding that there is a significant relationship between menstrual distress and marital dissatisfaction.4

So you can think of PMS as some sort of unconscious anger directed by a woman toward her partner for being unsuccessful in impregnating her.

There are a lot of unconscious processes by which a woman chooses her relationship partner. One way is assessing how the potential partner smells based on which her body makes decisions about a potential partner’s biological compatibility.5

If the function of period mood swings is to dissolve the current infertile relationship, the next logical step is to find new compatible partners

Just as when depression fades away when you begin to solve your complex life problem, if a woman is able to find a compatible mate, her PMS symptoms should ease.

A study found that when women were exposed to male perspiration, they experienced strong psychological effects- it improved their mood, reduced tension, and increased relaxation.6

The perspiration that the women were exposed to in the study was a mix of perspiration samples from different men. It’s likely that these women, out of the mix of different male pheromones, got exposed to the pheromones of a biologically compatible partner, thereby experiencing a reduction in their PMS-like symptoms.


  1. University Of California – Los Angeles. (2003, February 26). Birth Control Pill May Provide Relief For PMS. ScienceDaily. Retrieved November 19, 2017 from www.sciencedaily.com/releases/2003/02/030226073124.htm
  2. Dennerstein, L., Lehert, P., & Heinemann, K. (2011). Global study of women’s experiences of premenstrual symptoms and their effects on daily life. Menopause international17(3), 88-95.
  3. Gillings, M. R. (2014). Were there evolutionary advantages to premenstrual syndrome?. Evolutionary applications7(8), 897-904.
  4. Coughlin, P. C. (1990). Premenstrual syndrome: How marital satisfaction and role choice affect symptom severity. Social Work35(4), 351-355.
  5. Herz, R. S., & Inzlicht, M. (2002). Sex differences in response to physical and social factors involved in human mate selection: The importance of smell for women. Evolution and Human Behavior23(5), 359-364
  6. University Of Pennsylvania. (2003, March 17). Pheromones In Male Perspiration Reduce Women’s Tension, Alter Hormone Response. ScienceDaily. Retrieved November 19, 2017 from www.sciencedaily.com/releases/2003/03/030317074228.htm