When Hormones Change: Why Perimenopause and Menopause Cause Brain Fog and Low Mood — and What You Can Do

As women enter perimenopause and menopause, hormonal shifts — especially declines in oestrogen and progesterone— don’t just affect the body; they reshape the brain. Many women report brain fog, memory lapses, difficulty concentrating, low mood, and mental fatigue. This isn’t “just in your head” — the changes have a real biological basis. (The Menopause Charity)

How Hormonal Changes Affect the Brain

1. Oestrogen and Brain Function

Oestrogen acts as a neuromodulator - this is a fancy word for saying it helps the growth of new brain cells, protects against inflammation, improves blood flow, and regulates neurotransmitters, including serotonin, dopamine, and GABA. (PMC)

2. Oestrogen and Serotonin Signalling

Serotonin, the “feel-good” neurotransmitter, regulates mood, sleep, appetite, and cognition. Oestrogen influences serotonin in three main ways:

• Production: Oestrogen boosts the enzyme that converts tryptophan (an amino acid found in protein rich foods like poultry) into serotonin. Less oestrogen → less serotonin.

• Receptor sensitivity: Oestrogen maintains serotonin receptor density and responsiveness. Low oestrogen reduces efficiency.

• Reuptake: Oestrogen moderates serotonin reabsorption. When oestrogen drops, serotonin may be cleared too quickly from synapses (the spaces between brain cells)

Effect: Reduced oestrogen can lead to low mood, irritability, anxiety, sleep disruption, and cognitive changes, commonly reported during perimenopause and menopause. (Harvard Health)

3. Brain Metabolism and Cognitive Function

Oestrogen also supports the brain’s energy metabolism by helping brain cells use glucose efficiently and maintain neural connections. When oestrogen drops, brain energy slows, circulation may change, and synaptic density can decline. Studies show that up to two-thirds of women in perimenopause or menopause experience cognitive difficulties, including memory lapses, difficulty concentrating, and “mental fatigue.” (SpringerLink)

4. Menopause and the Brain: Evolutionary, Not Pathological

While brain fog, memory changes, and mood fluctuations during perimenopause are often seen as problems, researchers suggest these changes may actually be adaptive, evolutionary shifts, rather than purely pathological.

The “Grandmother Effect”

The grandmother hypothesis proposes that menopause evolved to extend a woman’s lifespan beyond her reproductive years to improve survival of her grandchildren. By shifting focus from bearing children to supporting kin, women could enhance family success and ensure their genes were passed on.

• Cognitive changes during menopause may reflect a shift in priorities and attention. For example, while verbal memory might decline slightly, social cognition, empathy, and emotional intelligence often remain intact or even improve. This could support caregiving roles and social coordination within multigenerational family groups. (Hawkes et al., 1998)

• Emotional reactivity and mood fluctuations may have evolved to alert women to environmental or social stressors in a way that promotes protective behaviours for grandchildren.

Why Brain Changes Aren’t Always Negative

• Some regions of the brain show plasticity and adaptation rather than decline. Neural networks may reorganise to support experience-based decision-making, planning, and social support roles.

• Menopause-associated sleep disruption, mood shifts, or lower fertility-related energy allocation may have historically redirected energy from reproduction to caregiving, increasing overall family survival.

In short: What looks like brain fog or mood swings today may reflect ancient adaptive strategies — the brain is shifting from reproductive to post-reproductive roles. Recognising this perspective helps reduce stigma and reframes menopausal changes as a natural life-stage transition rather than a dysfunction.

Supporting Brain Health Through Nutrition and Lifestyle

Even as hormones change, there are evidence-based strategies to support cognition and mood:

Nutrition:

• Stabilise blood sugar with balanced meals: protein, healthy fats, fibre, low-glycemic carbs (slow-releasing)

• Include omega-3s, antioxidants, and polyphenols to reduce inflammation and support circulation

• Support serotonin with tryptophan-rich foods (eggs, chicken, turkey, tofu, nuts) and co-factors (B6, magnesium, zinc)

Lifestyle:

• Regular exercise enhances circulation, neuroplasticity, and serotonin production

• Sleep hygiene: maintain a cool, dark bedroom, consistent schedule, and wind-down rituals

• Stress management: mindfulness, breathwork, or gentle yoga help stabilise mood

• Brain stimulation: reading, learning, and social interaction maintain cognitive function

Hormone Replacement Therapy (HRT)

For women with severe symptoms, HRT can help restore estrogen, indirectly supporting serotonin signalling, brain energy metabolism, and mood stability.

• Timing matters: Starting HRT around menopause may improve cognitive function and mood, while later initiation shows less benefit (PubMed)

• Personalised approach: HRT should be tailored based on health history, symptom severity, and risk factors (British Menopause Society)

Takeaway

Brain fog, memory lapses, and mood changes during perimenopause and menopause are common and biologically driven. Declining estrogen affects both serotonin signalling and brain energy metabolism, contributing to cognitive and emotional symptoms.

What helps:

• Balanced nutrition and blood sugar support

• Omega-3s, antioxidants, and brain-friendly foods

• Exercise, sleep, and stress management

• Brain stimulation and social engagement

• HRT when appropriate

With the right combination of lifestyle strategies and medical support, it’s possible to reclaim clarity, mood stability, and cognitive function during this natural transition.

Tailored support can be extremely valuable when going through hormonal changes. Please do get in touch to discuss how I can help you.