How do I know whether my mood swings are hormonal or something else?

The most reliable clue is the timing of your symptoms. Hormonal mood swings caused by PMS or PMDD occur exclusively in the second half of your cycle (the two weeks before your period) and disappear as soon as your period starts. Track your symptoms for at least two cycles in a diary or app: record your mood, irritability and any crying spells each day, and mark when your period begins. If you see a clear cyclical pattern, a hormonal cause is most likely. If the symptoms do not disappear after your period and you have them for almost the entire month, that points more toward depression or another mood disorder than toward PMS or PMDD.

How severe can these hormonal symptoms be? Mild mood swings around your period are very common, but some women are affected more seriously. Around 3 to 8 percent meet the criteria for severe PMS; approximately 2 percent have PMDD, a more serious form in which symptoms considerably disrupt daily life. PMDD likely also involves individual differences in brain reactivity: in some women, a rising hormone during the luteal phase actually triggers anxiety and mood symptoms, while in others it has a calming effect.

Around menopause (roughly between the ages of 45 and 55), mood swings can also be hormonal, but in this case they are caused by declining oestrogen. Even so, the cause here is rarely purely hormonal: sleep problems, pain and psychosocial changes almost always play a role as well. A cyclical pattern is therefore harder to recognise at menopause, because the menstrual cycle itself becomes irregular.

Are there blood tests that can help? Thyroid problems can affect mood, but the evidence for this comes from research in people under extreme circumstances; whether a mild decline in thyroid function causes everyday mood swings cannot be reliably determined from the available research. For bipolar disorder, large clinical studies have found hormonal and inflammatory markers that deviate from the norm, but these are only moderately discriminating and require specialist assessment. A self-test based on blood values is therefore not possible.