How does Motivation Shift across the Menstrual Cycle?
- Annalise Whines
- 6 hours ago
- 5 min read
Around menstruation, people may not lose motivation so much as raise the bar for what feels worth doing.
Premenstrual syndrome (PMS) refers to the emotional and physical changes many people experience in the days before a menstrual period, including anxiety, low mood, irritability, fatigue, and bloating. At its most severe, when symptoms are debilitating and interfere with daily life, it is known as premenstrual dysphoric disorder (PMDD).
Despite affecting an estimated 250 million people worldwide, we still do not fully understand why these symptoms occur, or why some people experience them much more intensely than others. These unanswered questions drive my PhD research at Cambridge, where I study the links between the menstrual cycle, motivation, and mental health.
What Happens Across the Menstrual Cycle?
The menstrual cycle is divided into two main stages: the follicular phase and the luteal phase, separated by ovulation.
The follicular phase is named after the follicle, a small fluid-filled sac in the ovary that contains an egg. As the follicle matures, it releases increasing amounts of oestrogen. When oestrogen reaches its peak, it triggers ovulation — the release of the egg.
If the egg is not fertilised, the body enters the luteal phase. During this stage, progesterone rises, alongside a smaller second increase in oestrogen. Then, in the days before menstrual bleeding begins, both hormones fall sharply.
Not everyone responds to these hormonal shifts in the same way. Some people are more sensitive to progesterone, others to oestrogen. Some are sensitive to both, and some to neither. The more sensitive someone is, the more likely they are to experience premenstrual mental health symptoms. My research looks at how oestrogen affects the brain and behaviour, which could help explain why these symptoms happen.
Why Focus on Oestrogen Sensitivity?
I'm particularly interested in oestrogen because the brain regions involved in motivation contain many oestrogen receptors. When oestrogen is high, it can increase dopamine in these regions. Dopamine is a key brain chemical that supports our drive to pursue rewards. It's what gets you out the door for a run even when you'd rather stay on the sofa. When oestrogen falls sharply before menstruation, this dopamine boost may weaken, potentially contributing to changes in motivation and mood.
How does Mood Shift with Oestrogen?
We studied the same participants at two key points in their cycle: the oestrogen peak around ovulation, and the sharp drop in oestrogen just before menstruation. Participants reported more mental health symptoms during the low-oestrogen phase. Low mood, heightened anxiety, and less enjoyment of things they usually liked were all more common at this time. These are experiences many people recognise in themselves, discuss with friends, or see reflected in conversations online.
What about Motivation?
Researchers often study motivation using effort-based decision-making tasks, where people decide whether a reward is worth the effort needed to earn it. Would you do 100 squats for £2? What about £5?
In our online version, participants helped feed a hungry octopus. Each round, they were offered some shrimp in exchange for clicking their mouse repeatedly. The number of shrimp on offer, and how fast and how long they had to click for, varied each round. We tailored the clicking to each person beforehand, so every offer was achievable. The question wasn't whether they could do it, but whether they wanted to. Participants could accept or reject each offer. If they accepted and clicked fast enough for long enough, they won the shrimp and fed the octopus. If they rejected, they still got a single shrimp.
We then used mathematical models to break motivation down into three parts: how willing people were to put in effort overall, how much rewards encouraged them, and how much effort put them off. For example, one person might click whether two or ten shrimp were offered, while another might only accept when the reward was large.
As predicted, participants were less willing to put in effort overall in the days around menstruation than around ovulation, no matter what the offer was. More unexpectedly, the size of the reward mattered more to them around menstruation. They were less willing to work for small rewards, like two shrimp, but still willing to put in the effort for larger rewards, like four or five. So, motivation didn't simply drop. Participants became more selective about what was worth their energy.
Crucially, the participants who became more selective also showed a smaller drop in mood during the premenstrual phase. This hints at a potentially protective response to the fall in oestrogen.
Direct evidence for this is still limited, but one plausible explanation involves energy conservation. The premenstrual phase can be physically demanding, with common symptoms including fatigue, disrupted sleep, headaches, and cramping. Becoming more selective about which efforts feel worthwhile may therefore be a way of spending energy more carefully when the body has less to give.
One way to think about it is like a phone switching into low power mode. As the battery runs down, the phone dims the screen, closes background apps, and prioritises essential functions. It still works, it just stops spending energy on things that are not necessary. The battery lasts longer and the important tasks still get done.
Something similar may be happening here. Choosing not to invest in low-reward tasks could be a way of protecting energy for what feels worthwhile. And that protection may, in turn, help buffer against low mood.
The reverse may also hold. If participants whose selectivity did not shift continued spending energy on low-reward demands, that ongoing expenditure could, over time, contribute to worsening mood. This remains a hypothesis rather than an established mechanism, and testing it directly is an important next step for future research.
Is Hormonal Sensitivity Always a Vulnerability?
Hormonal sensitivity is usually talked about as something that puts people at risk of premenstrual mood symptoms. Our study looked at people from the general population, not those with a diagnosis like PMDD, and the picture turned out to be more complex. For some people, becoming more selective about where to invest effort during the premenstrual phase may actually be adaptive.
The next step is to understand how these adaptive responses work. People with PMDD experience much more severe premenstrual mood changes. Does the same shift in selectivity happen in them, or is the pattern different? If the shift is absent, that could be part of what makes their premenstrual mood changes so severe. And if so, could therapy or medication encourage this shift, and help relieve symptoms? By identifying mechanisms that already protect some people, we may be able to extend that protection to many more.
