Perimenopause mood symptoms scored 1.5x higher in 20 countries

She is forty-three. Her periods are still arriving, more or less when expected. She has begun losing her temper at inanimate objects, sleeping in ninety-minute increments, and reaching for the word colander and not finding it. Hot flashes — the one perimenopausal symptom nearly everyone can name — have not arrived, so she files all of this under work stress, or parenting, or the general erosion of being in one's forties.

A new analysis, published online ahead of print on 28 July 2026 in Menopause: The Journal of the Menopause Society and pushed to the wires the following day as part of a series of papers from Flo Health and Mayo Clinic, is an attempt to give that woman a number. Researchers ran a cross-sectional survey through Flo, a cycle-tracking app, and included 7,975 users aged 35 and above who used the app in English, French, Portuguese or Spanish, spread across 20 countries on six continents. Women taking hormonal contraception or hormone therapy were excluded, which matters: both alter the symptoms being measured.

The instrument was the psychological domain of the Menopause Rating Scale, a validated questionnaire that asks about four things — depressive mood, irritability, anxiety, and physical and mental exhaustion. Each is rated from 0 to 4, so the domain runs from 0 to 16. The comparison was between women who said they were currently in perimenopause and women who said they were not.

The perimenopausal group averaged 7.3, the premenopausal group 4.8 — a gap of 2.5 points on a 16-point scale. The two groups were not, however, the same women six years apart in mood alone: the perimenopausal group averaged 45 years old, the premenopausal group 39. Age was adjusted for; it was not eliminated. Both groups also scattered widely around those means — standard deviation 3.56 in each — so the gap is roughly seven tenths of a standard deviation, and the two distributions overlap across most of the scale. It is a real difference in the average woman, not two separable populations.

Exhaustion showed the largest single-symptom difference — which is more interesting than it sounds, because the Menopause Rating Scale does not mean tiredness by that word. Its wording for physical and mental exhaustion is 'general decrease in performance, impaired memory, decrease in concentration, forgetfulness.' What the scale calls exhaustion is closer to what a reader would call brain fog — and the companion survey, which had room for a separate brain-fog item, found 87 percent of perimenopausal respondents endorsing that one too.

The difference held after adjustment for age, education, income, ethnicity, body mass index, smoking, alcohol consumption, and pre-existing anxiety or depression diagnoses. That last adjustment is the one worth pausing on: it means the gap is not simply an artifact of more women with psychiatric histories landing in the perimenopausal group. That reassurance is narrower than it first appears, because a prior diagnosis is not the same as a current illness, and adjusting for the diagnosis leaves undiagnosed depression sitting inside the estimate.

The companion paper from the same survey wave sets the context. Among 17,494 women from 158 countries surveyed between December 2024 and May 2025, hot flashes were the symptom most widely recognised as perimenopausal, at 71 percent. But among respondents aged 35 and over, the symptoms actually being reported were fatigue and physical and mental exhaustion, both at 83 percent, and irritability at 80 percent. The public script and the lived one are describing different conditions.

Here is the load-bearing weakness, and it is not the generic one. In this survey the exposure variable — perimenopause — was self-assigned. Women were shown a definition of reproductive stage and asked to place themselves. The companion paper concedes the consequence plainly: those definitions 'did not include changes in menstrual cycles, unlike those set out in the STRAW +10 criteria, which may have resulted in women misclassifying their reproductive stage.'

That creates a specific circularity rather than a vague one. A woman who feels irritable, foggy and low has a reason to go looking for an explanation, and perimenopause is currently the most available explanation on offer. A woman who feels well and cycles predictably has no such prompt and ticks no. Some portion of the 2.5-point gap is a difference between two symptom experiences; some portion is a difference between two self-diagnoses. Nothing in a cross-sectional design can separate them.

The scale of that ambiguity is visible in the companion paper's own figures: of 12,681 women aged 35 and over, only 21 percent said they were currently in perimenopause, 45 percent said they were not, and 33 percent said they did not know. This analysis makes the fate of that unsure third explicit in its own arithmetic — 2,353 perimenopausal women plus 5,622 counted as premenopausal, meaning self-reported neither perimenopausal nor postmenopausal, sum to exactly the 7,975 analysed. The undecided are not in the comparison at all, and where they belong would move the headline number in either direction.

The sampling compounds it. Everyone here had downloaded a period-tracking app, meaning a smartphone, data, and enough digital literacy to complete a long questionnaire. In the companion sample, 59 percent answered in English and 48 percent were White. The authors state that reliance on self-report 'introduces the possibility of reporting and selection bias, as women experiencing symptoms may have been more likely to participate.' A survey advertised inside a women's-health app is not a random draw of the world's midlife women; it is a draw of women already thinking about their bodies.

The most quotable result was the country league table. Nigeria recorded the lowest mean psychological score at 3.5; Brazil the highest at 8.8, with the United States at 7.9. The paper labels this analysis exploratory, and the label is doing real work.

The paper counts 2,353 perimenopausal women among the 7,975. Spread across 20 countries, that averages about 118 per country, and averages conceal their own tails — some national estimates will rest on far fewer. A four-language instrument then has to carry constructs like 'inner tension' and 'feeling aggressive' across cultures with different conventions about naming distress to a stranger. A 5.3-point spread between Nigeria and Brazil is at least partly a spread in what women in each place will say out loud.

The companion paper found a similar Nigerian pattern — under 60 percent reporting each of the top three symptoms, against over 80 percent in most other countries — but two analyses of the same survey agreeing is consistency, not independent confirmation. The wire coverage largely ran the table as a finding about countries. It is a finding about respondents.

Quite a lot, actually. The wires reprinted the release nearly verbatim under the phrasing 'mental health issues are 1.5x more severe,' which converts a mean difference on a self-rated ordinal scale into a claim about the severity of illness — a translation the study cannot underwrite. Nor was the analysis independent of its subject. Its co-first author is Flo's lead research scientist and the author the release calls senior is Flo's director of science; all eight authors of this paper also appear on the companion, whose disclosures list three of them — including both of those Flo scientists — as Flo Health employees or consultants holding equity in the company, alongside the Mayo Clinic co-authors.

But the direction is robust to all of that, and the practical content is unusually clear. The symptoms women rate as worst in this transition are mood, irritability and cognitive exhaustion — not the hot flash that 71 percent of women name when asked what perimenopause looks like, and which ranks eleventh of 26 on the list of what perimenopausal respondents actually report. The Flo co-first author frames it as symptoms that 'can have a real impact on daily life and work, and they deserve to be part of the conversation' — which is a claim about what belongs on a clinical agenda, not about causation, and on that narrower claim the data hold.

Every so often a study measures something women have been describing for decades and the measurement is still worth having. This is one: 7.3 against 4.8 on a 16-point scale, with cognitive exhaustion — impaired memory, lost concentration, the missing word — carrying more of the gap than either anxiety or low mood, and the effect surviving adjustment for income, education, BMI and prior psychiatric diagnosis. What it is not is evidence that perimenopause makes mental illness 1.5 times more severe, which is how the wires ran it. The women who counted as perimenopausal here decided so themselves, in the same questionnaire where they rated their symptoms, and feeling terrible is precisely what sends a woman looking for that label. The country league table should be read as scenery, not finding. The durable takeaway is narrower and more useful than the headline: in a very large international sample, the symptoms clustering around this transition are mood, irritability and mental fatigue — not the hot flash that 71 percent of women name when asked what perimenopause looks like — and they outrank it comfortably, in a group whose menstrual status the survey never asked about.