One of the least anticipated aspects of perimenopause is what happens to mental health. Women who have never struggled with anxiety suddenly find themselves lying awake at 3am with a racing heart. Women who have always managed stress effectively find themselves overwhelmed by things that previously felt manageable. Women who feel they have no reason to be sad find themselves in tears.
This is not weakness. It is biology.
The oestrogen-serotonin connection
Oestrogen has a direct regulatory effect on serotonin — the neurotransmitter most associated with mood stability, contentment, and resilience. When oestrogen levels fall or fluctuate, serotonin availability is affected. This is why perimenopausal mood changes feel different from ordinary stress: they often seem to have no psychological cause, because their cause is physiological.
Oestrogen also influences GABA, the brain's primary inhibitory neurotransmitter. GABA is what allows you to feel calm rather than anxious, to think rather than panic. When oestrogen fluctuates, GABA activity fluctuates with it.
What this looks like in practice
The mood changes of perimenopause can include:
Anxiety that arrives suddenly and feels disproportionate to circumstances. A heightened sense of dread, urgency, or not coping. Panic attacks, sometimes for the first time.
Irritability and anger that feel different from normal frustration — more reactive, less rational, harder to recover from. Many women describe feeling like they are watching themselves react and cannot stop it.
Low mood, tearfulness, or a flat, empty feeling — sometimes described as depression, though it may not meet clinical criteria and often fluctuates differently from a depressive episode.
Emotional sensitivity — feeling more easily hurt, more reactive to perceived criticism, more fragile in relationships.
Why this is frequently misdiagnosed
Women presenting with these symptoms in their forties are frequently assessed for depression or anxiety disorders and prescribed antidepressants, sometimes without a hormonal cause ever being considered. This is not always wrong — SSRIs do help some women with perimenopausal mood symptoms — but it means the underlying cause goes unaddressed.
What helps
HRT — particularly oestrogen — can significantly improve mood in perimenopausal women, often within weeks. For women who cannot or prefer not to use HRT, CBT is well evidenced for perimenopausal anxiety, aerobic exercise has a meaningful effect on mood, and SSRIs or SNRIs are used in some cases.
Most importantly: what you are feeling is real, it has a physiological explanation, and it is treatable.