Why women’s mental health symptoms often get worse in winter
Have you ever noticed that you struggle more with anxiety, low mood or motivation in winter - and wondered if it's all in your head? It's something I've noticed in myself, and I want you to know there is a very real physiological reason for it.
The connection between winter, hormones and mental health is something that doesn't really get enough attention - and for women in perimenopause, the impact can be particularly significant. In this post I’ll explain what's actually happening biologically, and what you can do nutritionally to support your mental health through the cooler months.
Why reduced sunlight affects more than just your vitamin D levels
Most people are aware of the connection between the sun and vitamin D, but sunlight exposure is also involved in other biological processes, including serotonin production and circadian rhythm regulation.
Reduced light exposure disrupts our circadian rhythm - the body's internal clock - which affects sleep, mood, energy and appetite. The pineal gland uses light cues to regulate melatonin production, and less daylight means this rhythm can become dysregulated, affecting sleep quality and mood in ways that many women don't immediately connect back to the change in season.
Vitamin D deficiency is also more common than most people realise, particularly in winter in the southern states and in women who spend the majority of their day indoors. In fact, you can be living in a sunny country like Australia and still be deficient - something that surprises a lot of my clients when they see their test results.
How sunlight and nutrients impact serotonin production
Serotonin is often called the "feel good" neurotransmitter and it plays a key role in mood regulation, emotional resilience, sleep and appetite. Sunlight stimulates the production of serotonin in the brain, so less light means lower serotonin, which directly affects mood, motivation and anxiety levels. Serotonin is also the precursor to melatonin, meaning low serotonin in the day can contribute to poor sleep at night.
Serotonin synthesis requires several key nutrients, including tryptophan, B6, folate, zinc and magnesium, so it makes sense that deficiencies in any of these can impair serotonin production (regardless of light exposure). Gut health is also an important consideration as approximately 90% of serotonin is produced in the gut.
Why women are more vulnerable to seasonal mood shifts
Women are significantly more likely than men to experience seasonal mood changes, particularly during perimenopause. Oestrogen plays a key role in how the brain produces and responds to serotonin - as oestrogen fluctuates and declines in perimenopause, serotonin sensitivity changes, making women more vulnerable to mood shifts. Progesterone levels also drop during perimenopause and many women experience increased anxiety, irritability and low mood as a result.
Midlife women are also more likely to be nutrient depleted going into winter due to the cumulative demands of stress, poor sleep and the physiological changes of perimenopause. This means that by the time winter arrives, many women are already running on empty - making the impact of reduced light and lower serotonin that much harder to cope with.
The role of vitamin D
Vitamin D deficiency is more common than most people realise - and you can be living in a sunny country like Australia and still be deficient, particularly in winter in the southern states or if you spend the majority of your day indoors. In Australia, the reference range for vitamin D is 50-70 nmol/L but the optimal level used by nutritionists, naturopaths and integrative GPs is 100 nmol/L. In clinic I regularly see women in their 40s and beyond falling well below this target, and low levels are associated with increased rates of anxiety, depression and poor emotional regulation.
Vitamin D receptors are found throughout the brain, including in areas involved in mood regulation, emotional processing and cognitive function. Vitamin D also influences the production of neurotransmitters and plays a role in regulating the HPA axis (the body’s stress response system), meaning low vitamin D can contribute to a heightened and prolonged stress response.
Other key nutrients that support mental health in winter
Beyond vitamin D, there are several other nutrients that play an important role in supporting mood, energy and emotional resilience through winter:
Omega-3 fatty acids (EPA and DHA) - essential for brain structure and function, with strong evidence for their role in reducing anxiety and depression. Found in oily fish, walnuts and flaxseeds
Magnesium - involved in over 300 biochemical reactions in the body, including nervous system regulation and the production of serotonin and GABA. Many women are deficient, particularly under stress
B vitamins - particularly B6, B12 and folate, - essential for neurotransmitter synthesis and methylation. B12 deficiency in particular is associated with low mood, fatigue and cognitive changes
Zinc - plays a key role in neurotransmitter function and the regulation of the stress response. Low zinc is associated with increased anxiety and depression
Iron - low iron is one of the most common and overlooked drivers of fatigue, low mood and poor concentration in women, and is worth checking if symptoms are present
Protein - adequate protein provides the amino acid building blocks for neurotransmitter production, including tryptophan for serotonin synthesis
Practical strategies to protect your mood through the cooler months
Get outside in natural light in the morning - light exposure within the first hour of waking helps regulate cortisol and serotonin rhythms
Have your vitamin D level tested - if deficient, consider supplementation (seek professional guidance)
Eat oily fish 2-3 times per week - sardines, salmon, mackerel and trout are all good options
Prioritise magnesium-rich foods, e.g. dark leafy greens, nuts, seeds and dark chocolate
Eat a protein-rich breakfast to support neurotransmitter production and stabilise blood sugar, which directly affects mood
Support your gut - include diverse plant foods and fermented foods where tolerated
Reduce alcohol - alcohol depletes B vitamins, disrupts sleep, increases cortisol and lowers serotonin over time
Ask your GP to check vitamin D, iron, B12 and thyroid function if you are consistently struggling with mood and energy through winter
If you've been struggling through winter and putting it down to just being busy, stressed or getting older, I hope this post has shown you that there is a real physiological basis for what you're experiencing - and that there's a lot you can do about it. Small, consistent changes to how you eat and how you support your body through the cooler months can make a big difference to how you feel.