She was forty-eight, ran a regional team for a financial services company, and had been seeing a psychiatrist for eighteen months for what had been diagnosed as anxiety disorder with mild depression. She was on an SSRI. It was helping, somewhat, but she still described a quality of mental life that she found alien to herself — difficulty concentrating, a flatness of motivation, an inability to retrieve words and ideas with the ease she’d always had. “I used to be sharp,” she said. “I don’t know what happened.”
I asked her about her periods. They had become irregular about two years ago.
Nobody had connected the two.
Brain fog is the symptom nobody takes seriously enough
The symptom I see most often in perimenopausal women that gets attributed to stress, overwork, or psychological disorder is cognitive change — specifically the constellation that has come to be called perimenopausal brain fog: difficulty with word retrieval, short-term memory lapses, reduced processing speed, difficulty concentrating under pressure, and a subjective sense of cognitive slowing that the women experiencing it find deeply distressing.
It is distressing partly because it is real and partly because the women it typically affects are the ones who have spent their entire adult lives trading on their cognitive performance. High-achieving, analytically oriented women in demanding careers or complex family roles are not imagining the change. They are documenting it accurately.
And they are almost universally told it is stress.
The neurological basis
The brain is an oestrogen-sensitive organ. This surprises many people, but oestrogen receptors are distributed throughout the central nervous system, including in the hippocampus — the primary seat of memory formation — and the prefrontal cortex, which manages executive function, working memory, and cognitive flexibility [1].
Oestrogen enhances cholinergic and serotonergic neurotransmission, promotes synaptic plasticity, supports neuronal repair, and has neuroprotective effects against inflammatory and oxidative damage. When oestrogen fluctuates erratically in perimenopause — which it does, swinging high and low unpredictably before declining — these neurological functions are destabilised.
The result is the symptom pattern my patients describe: not intellectual decline, but a changeability in cognitive sharpness that tracks with the hormonal fluctuations. Some days are fine. Others, the words don’t come, the concentration won’t hold, the mental load feels heavier than the circumstances warrant.
In my practice at SW1 Clinic, I now routinely ask about cognitive symptoms when I take a hormonal history. It is not because I treat brain fog with aesthetic medicine — I don’t. But because the full picture of a patient’s hormonal health shapes the conversation about what support she might need and whom she should be seeing.
Why it gets misattributed
The misattribution happens for several reasons, all compounding each other.
First, the timing. Perimenopause in most women coincides with a period of genuine life stressors — career peak, ageing parents, children in demanding educational phases, relationship changes. The stress is real. The cognitive symptoms that appear in this context are reasonably attributed to it.
Second, the episodic quality. Brain fog in perimenopause is not constant — it fluctuates with hormonal patterns. There are good weeks and bad weeks. This variability reinforces the stress narrative: “I’m fine when things are calmer, so it must be the pressure.”
Third, the cultural context. In Singapore and across East Asia, the presentation of psychological or cognitive symptoms to medical professionals carries social weight that affects what women report. “I’m stressed and finding it hard to concentrate” is socially acceptable. “I think something may be wrong with my brain” is frightening. “I’m perimenopausal and experiencing hormone-driven cognitive changes” is rarely in the vocabulary because the conversation about perimenopause doesn’t happen in most families.
A study published in Menopause specifically examined attribution of perimenopausal cognitive symptoms and found that Asian women were more likely to attribute cognitive changes to stress or personality than to hormonal factors, compared to Western cohorts — in part because awareness of perimenopause as a cause was lower [2].
The anxiety dimension
It is worth separating anxiety from brain fog, because they are related but distinct presentations.
Perimenopause-related anxiety tends to have a particular character: it is new-onset or significantly worse than baseline, often with a quality of physiological activation — racing heart, physical tension — that the patient finds disproportionate to the triggering situation. It worsens in the late luteal phase and in phases of low oestrogen. It improves somewhat with hormonal stabilisation.
This is different from anxiety disorder, though the two can coexist and the distinction is genuinely difficult to make clinically without a hormonal context. The problem is that the psychiatric system, which correctly identifies anxiety symptoms and offers treatment, frequently does so without assessing or addressing the hormonal substrate.
My patient who had been on an SSRI for eighteen months — not wrongly prescribed, because her anxiety was real and the SSRI was providing some benefit — had never had her hormones assessed. When we measured them and she started hormonal support, the cognitive symptoms improved within two months in ways the SSRI hadn’t addressed.
I want to be careful here: SSRIs are appropriate and effective for perimenopausal psychological symptoms in many cases. The point is not that they shouldn’t be used. It is that hormonal assessment should happen alongside psychiatric assessment — not instead of it.
What the research shows
Multiple longitudinal studies have now confirmed that cognitive changes in perimenopause are real, measurable, and specifically associated with hormonal fluctuation rather than chronological ageing alone [3]. The cognitive changes documented in neuropsychological testing during perimenopause tend to partially improve in postmenopause as hormones stabilise at a lower level — consistent with the dysregulation hypothesis rather than a simple decline narrative.
Studies on hormone therapy and cognitive function show the relationship is complex and timing-dependent. Oestrogen initiated early in the perimenopause-to-menopause transition appears to have neuroprotective effects; initiated many years after menopause, the benefit is less clear. This is the “window of opportunity” concept that has emerged from the WHIMS and other studies.
What you can actually do
If you are experiencing cognitive changes that you’ve attributed to stress, and you are in your 40s or early 50s, ask for a hormonal assessment that includes oestradiol, FSH, and progesterone. This is a reasonable first step before or alongside a psychiatric referral.
Tell your doctor specifically about the timing: whether symptoms are worse in certain parts of your cycle, whether there is associated sleep disruption, whether you have other perimenopausal symptoms. Context matters.
And find a physician who is prepared to integrate the hormonal picture with whatever other management you may be receiving.
The cognitive sharpness you’ve relied on all your life is not a casualty of ageing. It is a hormone-sensitive function that deserves the same systematic assessment we’d give any other symptom.
“I used to be sharp” is not an acceptable endpoint of a medical conversation. It is the beginning of one.
References
[1] Maki, P. M., & Sundermann, E. (2009). Hormone therapy and cognitive function. Human Reproduction Update, 15(6), 667–681. https://doi.org/10.1093/humupd/dmp022 [VERIFY — confirm before publishing]
[2] Tan, M. N., et al. (2012). Perimenopausal symptoms and management: A survey of Southeast Asian women. Climacteric, 15(2), 182–188. [VERIFY — confirm before publishing]
[3] Greendale, G. A., et al. (2009). Effects of the menopause transition and hormone use on cognitive performance in midlife women. Neurology, 72(21), 1850–1857. https://doi.org/10.1212/WNL.0b013e3181a71193 [VERIFY — confirm before publishing]
