Persistent Low Mood in Perimenopause: Possible Causes

Q: Can perimenopause cause depression even if you have never experienced it before?

Yes. Perimenopause can leave you more open to depression, and that includes times when you have no prior history of it. The hormonal changes of this phase, especially fluctuating oestrogen, can affect the brain chemicals that regulate your mood. If you think you may be experiencing depression, speak to your GP for a proper assessment.

Q: How is PMDD different from general perimenopause mood changes?

Premenstrual Dysphoric Disorder (PMDD) is a hormone-based mood disorder, where severe symptoms appear in the one to two weeks before your period and usually ease shortly after bleeding begins. General perimenopause mood changes tend to be less tied to your cycle and can feel more constant or more irregular. Because your cycle becomes less predictable in perimenopause, the difference is not always obvious. A GP or specialist can help clarify it through assessment.

Q: Could a thyroid problem be mistaken for perimenopause low mood?

It is possible. An underactive thyroid shares several symptoms with perimenopause, including low mood, fatigue, brain fog, and weight changes. If your symptoms have not lifted, or you are noticing this combination, it is worth asking your GP about a thyroid function blood test.

Q: What should you track in a symptom diary for low mood in perimenopause?

Useful things to note include the dates and severity of your low mood, any physical symptoms that come with it such as fatigue or brain fog, and where relevant, the dates of any cycle activity. Tracking over at least a full month gives your GP more to work with and can help bring out patterns that might point toward a specific cause.

Rest, menstruation and woman on couch with ibs, discomfort and stomach ache with symptoms. Health, fatigue and female person in house with cramps, endometriosis and abdominal pain for period.

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If a heaviness has settled in that does not seem to lift, or an irritability keeps catching you off guard, or most days just feel flat, these shifts are worth paying attention to. Persistent low mood during perimenopause can have several possible causes, and the general hormonal picture does not always explain all of it. Getting a sense of what might be driving how you feel is a useful starting point for a conversation with your GP.

How hormonal changes affect your mood

The low mood, anxiety, or irritability that can occur during perimenopause is closely linked to fluctuating hormone levels. As oestrogen and progesterone shift and gradually fall, these hormonal changes can affect the brain chemicals that regulate mood. When hormone levels become erratic, it can directly impact how you feel day-to-day.¹

Some weeks your mood might shift around with no clear pattern. Other times low mood feels more constant and sits with you most days. Either experience can be a sign that something beyond typical perimenopause is worth looking into.

How perimenopause can leave you more open to depression

Perimenopause can leave you more open to depression, even if you have never experienced it before. A passing low mood is different from depression, which is more persistent and brings a wider set of symptoms. Only a qualified healthcare professional can assess and diagnose depression, and it is worth seeking that assessment if low mood has stayed with you for two weeks or more, or if it is getting in the way of daily life.²

The hormonal changes of perimenopause can feed into this. Because perimenopausal symptoms and depressive symptoms overlap so much, telling them apart can be hard without professional support.

How PMDD can flare during perimenopause

If your mood drops sharply in the run-up to your period and lifts once bleeding begins, that pattern has a name. Premenstrual Dysphoric Disorder (PMDD) is a severe, hormone-related mood disorder where symptoms typically appear in the one to two weeks before your period and ease shortly after bleeding starts. For those with a history of PMDD, the fluctuating hormones of perimenopause may make cyclical symptoms feel more intense or unpredictable. Additionally, some people report experiencing PMDD-like mood shifts for the first time as their cycles change during this transition.³

Because your cycle can become irregular during perimenopause, it is easy to mistake worsening cyclical PMDD for a new, constant low mood. Tracking your mood against any cycle activity you still have can help make the pattern clearer. PMDD is not something to self-diagnose, and it needs assessment by a GP or specialist.

The thyroid overlap that is easy to miss

The low mood, fatigue, and brain fog you put down to perimenopause can sometimes come from your thyroid. An underactive thyroid (hypothyroidism) becomes more common in midlife and shares many of the same symptoms, including low mood, fatigue, weight gain, brain fog, and trouble concentrating. Because they overlap so closely, a thyroid issue can slip past unnoticed when everything gets attributed to perimenopause.⁴

If your low mood comes with these other symptoms, or your mood has not lifted with other perimenopause support, it is worth raising your thyroid with your GP. A simple blood test can check whether your thyroid is working within a normal range.

What a symptom diary can show you

Tracking your mood alongside any physical symptoms and any cycle dates you still have can make patterns easier to spot, and those patterns are worth discussing with your GP. A symptom diary can make a real difference to the quality of that conversation.⁵

Tracking can help show the shape of your low mood. If it is cyclical, that may point toward PMDD. If it is steady across the whole month, it may be worth exploring as depression or a thyroid issue. If it shifts irregularly, that lines up more with perimenopausal hormone changes. These are patterns to raise with a healthcare professional rather than conclusions to reach on your own.⁶

When to seek support for low mood in perimenopause

You do not need to have worked out the cause before you speak to your GP. If low mood has been with you for two weeks or more, is affecting your daily life, or comes with things like ongoing fatigue, trouble concentrating, or changes in weight, those are good reasons to seek an assessment. Your GP can look at the full picture, including whether hormones, depression, or your thyroid are worth investigating further or referring on.

What helps depends on what is behind it. Your GP might talk through options like hormonal support, thyroid treatment, talking therapies, or other approaches. These are decisions to make with professional assessment behind them.

If you are in immediate distress, call NHS 111 or contact the Samaritans on 116 123.

Frequently Asked Questions

Can perimenopause cause depression even if you have never experienced it before?

How is PMDD different from general perimenopause mood changes?

Could a thyroid problem be mistaken for perimenopause low mood?

What should you track in a symptom diary for low mood in perimenopause?

Sources

[1] Symptoms of menopause and perimenopause

During perimenopause, levels of oestrogen and progesterone fluctuate and gradually decline. Oestrogen plays a role in regulating neurotransmitters including serotonin and dopamine, both of which influence mood. When oestrogen levels become erratic, this can disrupt those chemical pathways, contributing to low mood, anxiety, and irritability.
[2] How can menopause affect my mental health?

Perimenopause is a period of heightened vulnerability to depression, including for those with no previous history of it.
[3] PMDD

If you have a history of PMDD, perimenopause may intensify your symptoms because the hormonal fluctuations of perimenopause can become more unpredictable. For some, PMDD-like symptoms can also appear for the first time during perimenopause.
[4] Thyroid and Menopause — British Thyroid Foundation

An underactive thyroid (hypothyroidism) is more common in midlife and shares several symptoms with perimenopause, including low mood, fatigue, weight gain, brain fog, and poor concentration.
[5] Symptoms of menopause and perimenopause

Tracking your mood alongside physical symptoms and any remaining menstrual cycle dates can make it easier to spot patterns that are worth discussing with your GP.
[6] Symptoms of menopause and perimenopause

Tracking can help distinguish whether low mood is cyclical (which may point toward PMDD), persistent across the whole month (which may be worth exploring as depression or a thyroid issue), or fluctuating irregularly in a way that aligns more closely with perimenopausal hormone changes.