What nobody has studied about your cycle
I asked Europe PMC how much research exists on 31 questions about the menstrual cycle, and how much of it was a real trial. The answers are not spread evenly, and the empty spots are the point.
papers on plastics, pollution and hormone disruptors affecting cycle mood. That is the whole literature.
randomized trials on the genetics of premenstrual symptoms, out of 168 papers. Genetics is the root of the whole thing.
more research on the cycle in animals (1,361) than on premenstrual self-harm and suicide (103).
There are also 88 papers on the moon and the menstrual cycle, and 40 on whether where you live changes your symptoms.
Every topic, and how much of it got tested
Each row is one search. The purple dot on the right is how many papers exist. The green dot on the left is how many were real trials. The space between them is the gap.
On a phone, scroll the chart sideways. Every number is in the table below.
The numbers
| Topic | Papers | Trials and reviews | Share |
|---|---|---|---|
| Environmental | 3 | 0 | none |
| Geographical | 40 | 2 | 5.0% |
| Menstrual synchrony (myth) | 43 | 2 | 4.7% |
| Lunar / moon myth | 88 | 0 | none |
| Self-harm / suicidality | 103 | 7 | 6.8% |
| Relationship status | 126 | 5 | 4.0% |
| Genetic | 168 | 0 | none |
| Ethnic / cultural | 172 | 2 | 1.2% |
| Evolution of menstruation | 187 | 4 | 2.1% |
| Spending / decisions | 211 | 18 | 8.5% |
| Confidence / self-esteem | 229 | 47 | 20.5% |
| Seasonal | 399 | 17 | 4.3% |
| Reproductive physiology | 425 | 21 | 4.9% |
| Workplace / productivity | 540 | 50 | 9.3% |
| Hormonal | 588 | 72 | 12.2% |
| Occupational | 632 | 27 | 4.3% |
| Relationships / partners | 789 | 40 | 5.1% |
| Cravings science | 810 | 93 | 11.5% |
| Athletes / performance | 827 | 63 | 7.6% |
| Sleep / dreams across cycle | 923 | 64 | 6.9% |
| Nutrition | 1,298 | 161 | 12.4% |
| PMS in animals | 1,361 | 19 | 1.4% |
| PMDD | 1,500 | 171 | 11.4% |
| Gut microbiome x cycle | 1,600 | 61 | 3.8% |
| Insulin resistance | 1,772 | 135 | 7.6% |
| Pain across cycle | 2,185 | 228 | 10.4% |
| Inflammation | 2,200 | 99 | 4.5% |
| Symptoms / cycle mood | 2,561 | 307 | 12.0% |
| PMS | 3,655 | 374 | 10.2% |
| Positive / luteal upside | 3,705 | 202 | 5.5% |
| History of PMS | 5,167 | 192 | 3.7% |
How I counted, and what this is not
Each topic is one search I ran against Europe PMC on August 16, 2026, matching on title and abstract. The number is that search's total hit count. "Trials and reviews" is the same search, filtered to randomized controlled trials, meta-analyses and systematic reviews.
This is not a systematic review, and a search is only ever a rough proxy. Word it broadly and you get more back. Word it narrowly and you get less. So read these as the shape of a field, not an exact count. I ran the same method on every topic, so comparing one row to another is fair even where a single number is rough.
I left out 27 other searches about women at work, because those are not cycle-specific and the numbers are not comparable to these.
This is why I grade everything
When a field is this thin, confident advice is the warning sign. Niyora shows you the evidence behind every claim it makes, including the weak stuff.