You Didn’t Go Flat. Your Immune System Got Loud.
The Body · The Reading Room, Vol. 16 · 10 min read · What twenty-one years of SWAN data show about inflammation at the transition, what two controlled trials proved and did not prove, and the week of notes worth taking before your appointment
The mood dip gets filed under hormones and closed. Inflammation and mood in menopause turn out to be linked too, and your immune system does not stay quiet about it.
You cancelled the dinner again. Nothing happened. You looked at the calendar entry, the friend’s name, the restaurant you picked together back in June, and felt none of the pull you used to feel towards things you like. Not sad exactly. Not anxious either. Just flat, the way a drink goes flat: still technically the same drink.
Your doctor asked about your cycle and your sleep and wrote “perimenopausal” in the chart. Nobody asked about the blood work from March, where a nurse mentioned, almost in passing, that your inflammation markers ran a little high for someone your age.
What follows is a reading of published epidemiology and controlled trials on that flatness. I am not a clinician, the findings belong to the researchers named below, and only the plain-English version is mine.
The short answer: the flatness of midlife is not only hormonal. For decades oestrogen has been doing a second job — holding inflammatory signalling down — and as it falls, that restraint goes with it. Call it the lifted brake. Markers like CRP and interleukin-6 tend to rise across the transition, and those same molecules act on the brain circuits that govern mood, motivation and energy. It is a third, measurable mechanism, distinct from both “it’s your hormones” and “it’s all in your head.”¹²³
The skim version
- Oestrogen has a second job beyond cycles and hot flushes: keeping inflammatory signalling turned down.¹
- In a 21-year SWAN analysis of more than 1,400 women, interleukin-6 rose sharply in the year before and the three years after the final period.¹
- In a separate study of 3,292 women in the same transition, depressive symptoms tracked with inflammatory markers, not hormone levels alone.²
- Controlled trials show the direction of cause: give healthy volunteers a small inflammatory challenge and mood drops, with women affected more than men.⁴
- But a 2025 trial found that effect in women aged 25 to 44 and not in women aged 60 to 80 — which is an honest complication, not a footnote.⁵
- Five common conditions produce exactly this flatness and are cheaper to rule out first. They are in the differential below.
The source for this piece
Prof. Samar R. El Khoudary, PhD, MPH
An epidemiologist who has spent her career on what the menopause transition does to a woman’s cardiovascular and metabolic health, working with the Study of Women’s Health Across the Nation at the University of Pittsburgh’s Epidemiology Data Center, and elected to the board of the North American Menopause Society. She led the analysis that established when in the transition inflammatory markers actually move — which is the finding this article rests on, and the reason it can name a window rather than gesture at “midlife”.
What we read: El Khoudary et al., Journal of Clinical Endocrinology & Metabolism (2025), alongside Matthews and colleagues in Psychosomatic Medicine (2007) and two endotoxin trials from the UCLA group.¹²⁴⁵
Where to follow her work: UPMC expert profile · ResearchGate · The SWAN study
What is the link between inflammation and mood in menopause?
Inflammation and mood in menopause are connected through a job oestrogen has been doing quietly for decades: keeping low-grade inflammatory signalling turned down. Oestrogen has receptors on immune cells themselves, and for most of adult life it dampens the production of inflammatory messengers. When oestrogen falls, that dampening falls with it.
Researchers with the Study of Women’s Health Across the Nation, known as SWAN, tracked more than 1,400 women for up to 21 years, drawing blood at as many as fifteen points along the way. Interleukin-6 rose sharply in a window running from about a year before the final period to three years after it, and the rise was steepest in women who had not already been running high. C-reactive protein followed a milder version of the same pattern.¹
None of this happens overnight, which is part of why it gets missed. The SWAN data traces a multi-year window, not one bad month, and nothing about it announces itself the way a hot flush does. There is no single morning where the immune system visibly changes gears.
This is the same hormonal shift already familiar as the mechanism behind new anxiety that shows up with no history of it. Inflammation is a parallel piece of that picture, running alongside the anxiety mechanism rather than replacing it.
Why does the immune system change at menopause?
Because the brake was hormonal, and the brake has lifted. Immune cells carry oestrogen receptors, and oestrogen normally tells those cells to stand down. Remove enough of it and the immune system’s baseline drifts upward, the way a thermostat set two degrees higher runs the furnace more often without anyone touching the dial.
Definition: low-grade inflammation is a persistent, mild rise in immune markers such as CRP and interleukin-6 — well below what an infection or injury produces, but sustained over months and years, and high enough to influence brain chemistry, energy and mood.
Inflammatory signalling does something else worth naming. It can produce a low-energy, low-motivation, withdrawn state — the one your body manufactures on purpose when it is fighting an infection.³ For a week of flu, that response earns its keep: it gets you into bed and away from other people until it passes. When the trigger is a slow hormonal shift rather than a virus, the same machinery can switch on with nothing around to switch it back off, and the flatness simply continues, month after month, with no fever to explain it.
It is not confined to mood, either. The same inflammatory shift is part of what is now understood about joint pain that starts in perimenopause with nothing to show on a scan. Mood, joints and energy are different rooms in the same house, and this is plumbing that runs through all of them.
If you are already keeping a private tally of which symptom belongs to which explanation — the hormone one, the sleep one, the mood one, and now this one — the Quiet Audit is a ten-minute way to put the whole list on one page before you try to explain any of it out loud. Nobody sees your answers. Start here.
Between us — what the research found
Four sources sit under this and I want you to see their edges. SWAN followed more than 1,400 women through the transition and found interleukin-6 rising sharply around the final period in women who had not already been running high.¹ A separate SWAN analysis of 3,292 women found depressive symptoms tracking with inflammatory and clotting markers over time rather than with hormone levels alone.² A review of the inflammation-and-depression literature found inflammatory signalling acting on the brain circuits behind motivation and energy, concentrated in people already carrying other risk factors.³ And two randomised controlled trials gave healthy volunteers a small inflammatory challenge and watched mood move within hours.⁴⁵
The limitation, stated plainly: the observational work shows inflammation and mood moving together across large groups, not that one causes the other in any single woman. Interleukin-6 could not be measured in every SWAN participant, for budget reasons, which shrinks that sample. And the causal trials do not line up neatly with this readership: the 2015 trial ran in healthy adults with an average age in the twenties and thirties, and the 2025 trial found the mood effect in women aged 25 to 44 but not in women aged 60 to 80.⁴⁵ Nobody has run this trial in women aged 45 to 60, which is exactly the group reading this. What we have is strong evidence that the mechanism exists, good evidence that the markers rise at the transition, and an untested gap in between. We are not going to pretend that gap is closed.
Five Things That Look Like This and Are Not This
Everything above assumes flatness with no other explanation on the table. Often there is one, and it is cheaper and faster to rule out than anything involving inflammatory markers. Ask about these five before you ask about CRP.
- An underactive thyroid. Flatness, cold, weight change, slowed thinking — it produces this picture almost exactly, is far more common in women over 45, and is a standard blood test that most surgeries will run without an argument.
- Low iron stores. Heavy or erratic perimenopausal bleeding depletes iron long before it shows as anaemia. Ask for ferritin specifically, not just a full blood count, because ferritin can be low while the haemoglobin still reads normal.
- Vitamin B12 or vitamin D deficiency. Both are common after fifty, both produce fatigue and low mood, and both are more likely if you take metformin, a long-term acid-reducing medicine, or eat little animal protein.
- Sleep apnoea. The risk rises sharply in women after menopause, and in women it often presents as flatness, morning headache and fatigue rather than the loud snoring the stereotype expects. It is frequently missed for years.
- Clinical depression. Sustained hopelessness, loss of self-worth, no lighter days at all for weeks. That needs treating in its own right whatever your CRP says, and the pattern that separates it from perimenopause is shape and timeline more than intensity.
None of these rules out the inflammatory picture. They mean the mechanism in this article is the interesting question, not the first one, and a good appointment covers the cheap ground first.
Who Else Has Measured This
One cohort study shows two things moving together; it takes other work to show which way the arrow points. Three lines converge here.
The epidemiology. Karen Matthews and colleagues, including Joyce Bromberger, followed 3,292 women through the menopause transition and found depressive symptoms tracking with inflammatory and haemostatic markers over time, rather than with hormone levels alone.² Large, longitudinal, and pointed at the same window SWAN later mapped.
The causal trial. Mona Moieni, Michael Irwin, Naomi Eisenberger and colleagues at UCLA ran a randomised, double-blind, placebo-controlled trial in 115 healthy adults, giving half of them a small dose of endotoxin to raise inflammation for a few hours. Women showed greater increases in depressed mood and in feelings of social disconnection than men, and rises in interleukin-6 and TNF-alpha correlated with social disconnection in women but not in men.⁴ This is the leg the observational data cannot provide: inflammation went up first, and mood followed.
The age complication. A 2025 trial in Translational Psychiatry ran the same challenge in 93 women — 40 aged 25 to 44 and 53 aged 60 to 80. Depressed mood rose in the younger group and did not move in the older one, though a deficit in reward learning showed up in both.⁵ Read honestly, that says the mood effect is demonstrated in younger women and has not been demonstrated in older ones. Whether the transition years sit with the first group or the second is, at the moment, unknown.
An epidemiological signal, a controlled trial establishing the direction, and a second trial saying plainly where the effect has and has not been shown. That is what the evidence is, and it is more useful than a tidier version would be.
Flat is a signal, not a flaw.
Is this the same as depression, or something else?
Sometimes yes, sometimes no, and the pattern tells them apart rather than the feeling itself. Inflammation-linked flatness tends to move with the biology: it can ease on better-sleep weeks, worsen around a flare of joint pain or hot flushes, and rarely comes with the sustained hopelessness or loss of self-worth that marks clinical depression. The pattern that separates perimenopause from depression is timeline and shape more than intensity, and inflammation adds one more thread to it rather than a separate diagnosis.
Put the three explanations side by side and the gaps get easier to see.
| The explanation | What it gets right | What it misses |
|---|---|---|
| “It’s just hormones” | Oestrogen and progesterone shifts are real, measurable and timed closely to your symptoms | Why flatness specifically, rather than only mood swings or hot flushes |
| “It’s all in your head” | Nothing measurable | The blood chemistry that has actually shifted underneath it |
| “It’s inflammation too” | Matches the SWAN data on rising CRP and interleukin-6 at the transition¹ | Still one factor among several, and untested in this exact age band |
When this needs a doctor this week rather than a search bar
Book an appointment if the flatness has lasted more than two weeks without a single lighter day; if sleep or appetite has changed sharply alongside it; if your ability to function at work or at home has genuinely dropped; if you are waking two hours early with the day already dreaded; or if you have stopped wanting things you used to want rather than merely being too tired for them. Bring the blood work question with you — CRP is a standard, inexpensive test, and a high result at midlife deserves a direct conversation rather than a guess. If you are having thoughts of harming yourself, speak to someone today rather than reading further.
What This Actually Changes
Not the flatness, this week. Naming a mechanism does not lift it, and anyone promising that is selling something.
What it changes is the verdict underneath it. You have been treating the absence of pull towards a dinner you chose in June as information about your character — that you have become someone who does not want things any more. There is a measurable shift running through your body across exactly these years, it acts on exactly the circuits that produce wanting, and it has nothing whatsoever to do with how much you care about your friend.
It also changes what an appointment can be. “I have been feeling flat” gives a doctor almost nothing to work with in seven minutes. A week of two-word notes, a named question about the March blood work, and the four cheap tests from the differential give the same appointment a shape.
What to Say at the Appointment
The aim is not to arrive with a theory. It is to arrive with observations and one specific question, so the seven minutes go on decisions rather than on reconstruction.
Short enough to read off a phone screen
Open with the observation, not the theory: “For the last two months I have been flat rather than low. I have written it down for a week — here it is.”
Then the specific question: “My inflammatory markers were flagged as slightly high in March. Is that worth rechecking alongside thyroid, ferritin, B12 and vitamin D?”
If it gets closed down as “just the menopause”: “I understand that is likely part of it. I would still like the other four ruled out, and I would like that noted.”
If hormones, sleep, mood and this fourth thing have all become tangled together in your head, the Quiet Audit is a private ten-minute pass through the whole picture before your appointment rather than after it. Start here.
Questions women actually ask about this
Does inflammation cause depression at menopause?
Not on its own, and not for everyone. Controlled trials show inflammation can lower mood within hours in healthy volunteers, with women more affected than men.⁴ Cohort studies show markers rising across the transition and tracking with depressive symptoms.¹² What nobody has yet shown is that one causes the other in women of exactly this age, and a 2025 trial found the mood effect in younger women but not in women over sixty.⁵
Can a blood test actually show this?
CRP is a standard, inexpensive test many doctors already run. On its own, a high result at midlife is just a number. Paired with weeks of documented flatness and the cheaper causes ruled out, it becomes a specific question rather than a vague one.
Should I ask for a CRP test first?
Probably not first. Thyroid, ferritin, B12 and vitamin D are cheaper, more commonly abnormal in women over 45, and more directly treatable. CRP is worth adding to that list rather than leading with it.
Does hormone therapy lower inflammation?
The research here is still developing and not settled enough to promise anything, and the effect appears to differ by route and formulation. This article is not a treatment guide. If you are weighing hormone therapy, that conversation belongs with your own clinician, with your full history on the table.
Is flatness the same as being unmotivated by choice?
No. A body running a low-grade inflammatory signal is not a body that has simply stopped trying. The distinction matters less for assigning blame, which was never useful, and more for what you do next: naming a mechanism rather than grading your own character.
The one move
Anchor this to a moment you already have: the kettle boiling, or the last light switched off. For one week, write two words on your phone before you sleep — how flat, and how slept. Not an essay, not a mood app with a streak to keep.
A week of the same two words, in the same shape, changes what a seven-minute appointment can do with your time. It converts a feeling into a record, and records get taken seriously.
Where to Go Next
In order, and each for a reason.
1. The pattern that separates perimenopause from depression — the distinction that decides what kind of appointment you need.
2. Then new anxiety with no history of it, which runs on the neighbouring mechanism.
3. Then joint pain with nothing to show on a scan, if the flatness arrived alongside stiffness in the mornings.
Nobody asked about the March blood work. That is the question you are now able to ask, in one sentence, with a week of notes behind it.
References
1. El Khoudary, S. R., et al. (2025). The relation between systemic inflammation and the menopause transition: The Study of Women’s Health Across the Nation (SWAN). The Journal of Clinical Endocrinology & Metabolism, 110(11). Read the study
2. Matthews, K. A., Schott, L. L., Bromberger, J. T., Cyranowski, J., Everson-Rose, S. A., & Sowers, M. F. (2007). Associations between depressive symptoms and inflammatory/hemostatic markers in women during the menopausal transition. Psychosomatic Medicine, 69(2), 124–130. Read the study
3. Kiecolt-Glaser, J. K., Derry, H. M., & Fagundes, C. P. (2015). Inflammation: depression fans the flames and feasts on the heat. American Journal of Psychiatry, 172(11), 1075–1091. Read the study
4. Moieni, M., Irwin, M. R., Jevtic, I., Olmstead, R., Breen, E. C., & Eisenberger, N. I. (2015). Sex Differences in Depressive and Socioemotional Responses to an Inflammatory Challenge. Neuropsychopharmacology. Read the study
5. Boyle, C. C., et al. (2025). Inflammation-induced depressed mood and reward responsivity as a function of age in female adults: a randomized controlled trial of endotoxin. Translational Psychiatry. Read the study
On the researchers. Samar El Khoudary is an epidemiologist; Karen Matthews and Joyce Bromberger are academic researchers in psychiatry and epidemiology; Naomi Eisenberger and Michael Irwin lead laboratory work on inflammation and behaviour at UCLA. None of them is your clinician, and nothing in their published work is advice about your case. We link a university-hosted profile, ResearchGate and the SWAN study site for Professor El Khoudary rather than a LinkedIn page, because more than one profile carrying her name is in circulation and we do not link a profile we cannot verify. All five studies are linked in full above, with sample sizes, ages and designs stated in the body rather than buried.
Sourcing, disclosure and disclaimers
This is not medical advice. Blue Leaf Journal publishes general information for a general readership. Nothing here is a diagnosis, a treatment recommendation, or guidance about your medication, your hormone therapy or your test results. Which tests are available to you, and on what terms, differs by country and by practice.
We are not clinicians. Blue Leaf Journal is an independent publication. We read published research and translate it. The findings belong to the researchers and institutions named and linked above; the plain-English rendering is ours, and so is any error in it.
No affiliation and no endorsement. Blue Leaf Journal is not affiliated with Samar El Khoudary, the SWAN study, the University of Pittsburgh, UPMC, UCLA or the North American Menopause Society. None of them has reviewed, approved or endorsed this article, and none of them is responsible for it.
No commercial relationship. Nobody named above paid for or was paid for this coverage. There are no affiliate links, no sponsored placements, no supplement recommendations and no gifted products in this article.
How this was checked. All five studies are linked in the references with journal, year and sample details in the body. Where the causal trials do not cover women aged 45 to 60 — which they do not — we have said so in the body rather than implied otherwise. Sources were checked on 28 August 2026. If you find something we have got wrong, write to norawhitfield@blueleafjournal.com and we will correct it and say that we did.
Nora Whitfield writes the Body desk at Blue Leaf Journal: the biology of midlife in plain language, with the actual studies named rather than gestured at. She has cancelled a dinner she wanted to go to and then spent the evening deciding what that said about her. It said the same thing her March blood work said, which she had not read.
Written by Nora Whitfield for Blue Leaf Journal. Updated: 28 August 2026.
