It’s not just hormones: the real reasons your mood changes in your 40s

Are you a midlife woman experiencing mood changes such as low mood, anxiety, rumination and irritability? Well, that will be your hormones – as you’ve probably had enough people tell you by now. But sometimes women aren’t sure whether they’re in perimenopause, or fear there are other emotional issues at play.

Sadly, all too often women opt to, or are advised to, 'just get on with it', perhaps offered HRT (which can be of real benefit), or a prescription for antidepressants. Nearly half of women aged 45 to 54 who received a mental health diagnosis during the menopause transition are prescribed antidepressants, one survey found. Another revealed that 39% of women seeking help for perimenopausal symptoms are offered antidepressants instead of HRT as a first course of treatment, and some were offered two or three different types before anyone considered their hormones as a root cause.

What's happening in your brain?

In perimenopause, all our sex hormones start to decline, but not at the same rate, which is why this life stage can feel like a rollercoaster.

Progesterone is typically the first to drop, often in your late 30s or early 40s. It's our calming, stabilising hormone, helping with sleep and reducing anxiety. Crucially, progesterone receptors are found in virtually every major organ, including the brain, which is why its decline has such wide-ranging effects. The added importance of progesterone is that it binds to GABA receptors in the brain. GABA (gamma-aminobutyric acid) is your nervous system's brake pedal. When it's working well, you feel calm and able to switch off, but when it's not, you feel wired, anxious and unable to relax no matter how much you meditate or do breathwork. Sound familiar?

Oestrogen also has a profound effect on our brain chemistry. It boosts serotonin (the ‘happiness’ hormone) and the sensitivity of our serotonin receptors, supports dopamine (the neurotransmitter of motivation and pleasure), and regulates noradrenaline, which governs alertness and our stress response (part of our innate fight-and-flight mechanism). But it also has anti-inflammatory effects on the brain, protecting against depression and cognitive decline.

Finally, there's testosterone, often overlooked in women's health. It drives ambition, supports memory and executive function, and buffers against stress. As it falls, women can feel overwhelmed, indecisive and like they're losing their edge.

When stress takes over

The combination of hormonal changes causing destablisation, anxiety, reduced pleasure and reduced protection against depression and stress is pretty strong stuff in itself. But add in the typical strains of midlife women, and many are at breaking point.

As a nutritionist specialising in mental health for midlife women, I see this hormonal change compounded by the life many women are living at this age – balancing career, family and social life, and running on high stress. I've seen stress take the blame countless times when in fact perimenopause was starting to ramp up. Many women in their early 40s simply don't consider that their mood could be hormonal. I can put my hand up to this myself. At 40, I was burning the candle at both ends, blaming burnout, and not once considered my hormones. Looking back, the signs were clear.

HRT can play a vital role for some women, but it's not the answer for everyone. I see women in my clinic who have been on HRT for years, or those who couldn't get on with it, and both are still struggling emotionally. What's often missing are the macro and micronutrients needed for real hormone and neurotransmitter health. Hormones, even in HRT form, don't work in isolation, but need nutritional support. For example, oestrogen needs vitamin D, iron, B vitamins, magnesium and zinc to support serotonin production. And those all-important brain chemicals (serotonin, GABA and dopamine), are all made from amino acids. In other words, protein. If your diet is lacking these nutrients, all the HRT in the world won’t bring you back into a hormonal balance.

Why diet is the overlooked option

Nutritional psychiatry is a growing area of science that examines the relationship between what we eat and our mental health. Nutrient deficiencies, poor dietary habits and gut dysfunction can directly cause or worsen depression, anxiety and brain fog.

You may have heard of the gut-brain axis, but here’s how it directly affects your mental health. Your gut produces around 90% of your body's serotonin, and your gut microbiome regulates inflammation, hormone metabolism and neurotransmitter production. A disrupted microbiome caused by processed food, chronic stress or antibiotic use can significantly worsen the psychological symptoms of perimenopause. Blood sugar stability matters too, for as oestrogen falls, blood sugar regulation becomes less efficient, leading to energy crashes, mood dips and cortisol spikes that amplify anxiety and poor sleep. I often see midlife women being low in the specific nutrients vital for optimal brain chemistry, such as magnesium, folate, B6, omega-3s and zinc.

The top 5 foods to support your hormones and your mood

Protein (eggs, fish, poultry and meats, Greek yogurt, lentils, tofu). The raw material for every neurotransmitter in the brain including serotonin, dopamine, GABA. Protein needs to increase in midlife as the body becomes less efficient at using it. Spread sources across the day for best absorption. Aim for 25-30g at every meal
Oily fish (salmon, mackerel, sardines, anchovies). Rich in omega-3 fatty acids, the building blocks of brain cell membranes and powerful anti-inflammatory agents, regularly linked to lower rates of depression and improved cognitive function. Aim for two-three portions a week.
Leafy greens (spinach, kale, rocket, watercress). Packed with magnesium, folate and B vitamins that are essential for mood-regulating neurotransmitters. Magnesium also calms the nervous system, reduces cortisol spikes and may support better sleep. Aim for two-four cups a day.
Fermented foods (live yogurt, kefir, kimchi, sauerkraut, miso). Introduce beneficial bacteria to the gut microbiome, supporting the gut-brain axis and the gut's ability to produce serotonin and regulate inflammation, both of which are directly linked to mood. Aim to include a fermented food daily.
Legumes (lentils, chickpeas, black beans, edamame). An excellent source of fibre, which feeds our beneficial gut bacteria, alongside plant protein and B vitamins. High-fibre diets are associated with lower rates of depression, and legumes help stabilise blood sugar throughout the day. Aim for half a cup a day.

The many reasons your mood changes in your 40s – and it's not just your hormones

How to change your diet to fix your mood

This is not a quick fix, and I say that to every client. So many women arrive in my clinic having been sold the promise of a supplement or superfood by a clever marketing campaign or a well-meaning influencer. But when it comes to mental health, what I see working time and again is consistency: small changes that become the new normal, like starting every day with a protein-based breakfast rather than skipping meals or running on caffeine until noon. When clients commit to this kind of sustained shift, their mood stabilises, sleep improves, anxiety reduces, and low mood starts to lift. Most see meaningful change within six to 12 weeks.

The best time to start is before significant symptoms take hold and the brain changes of early perimenopause can begin well before anything obvious, sometimes as early as the late 30s. Building good nutritional habits before symptoms escalate means you're working from a stronger foundation. But it's never too late. Women in their 60s and beyond can still improve their mood and cognitive function through nutrition. The body is remarkably responsive when given what it needs.

More broadly, it's time for women's hormonal healthcare to evolve. The conversation cannot be limited to HRT versus antidepressants, important as both can be in the right circumstances. It must include sleep, movement, stress management and centrally, food. These are not soft or secondary interventions. They are not the 'nice to haves' that get mentioned at the end of a consultation. They are the biological foundations that perimenopause disrupts, and that targeted, consistent nutrition can genuinely help rebuild.

What you eat matters, and it's about far more than weight or hunger. Every time you eat is an opportunity to support your brain, your hormones and your mood.

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