PMS versus PMDD
PMS is common — most menstruating people experience some premenstrual symptoms. PMDD is severe premenstrual mood disturbance meeting specific diagnostic criteria: significant mood symptoms in the second half of the cycle, resolving after menstruation begins, affecting function meaningfully, for most cycles over the past year. PMDD affects a smaller proportion of the population and warrants specific treatment.
Continuous versus intermittent SSRI dosing
For PMDD, two dosing strategies are supported by evidence: continuous SSRI use (every day, as with standard depression treatment) or intermittent dosing (only in the second half of the cycle, from ovulation to menstruation). Both approaches show benefit. Intermittent dosing reduces overall medication exposure and may reduce side effects but requires accurate cycle tracking. Continuous dosing is simpler and may be preferred for people with mood symptoms outside the premenstrual window.
What the evidence supports
SSRIs typically show benefit for PMDD faster than for depression — often within the first cycle rather than requiring four to six weeks. Effect sizes in randomised trials are meaningful. Multiple systematic reviews support this indication. Your prescriber can advise which approach fits your situation. Tracking symptoms across two to three cycles before starting helps confirm the pattern and measure response.
What to flag to your prescriber
- Severe premenstrual mood symptoms affecting relationships or work.
- Suicidal thoughts appearing predictably in the premenstrual window.
- Cycle tracking that reveals patterns you had not noticed.
- Any concern that the diagnosis of PMDD versus another condition needs clarification.
Related reading: Antidepressants and the Menstrual Cycle and Antidepressants and Menopause.
Frequently asked questions
Do antidepressants help with PMS?
For severe PMS meeting PMDD criteria, SSRIs are first-line treatment with strong evidence.
Can I take antidepressants only around my period?
Yes — intermittent dosing (second half of the cycle only) is a supported approach for PMDD, alongside continuous dosing.
How quickly do antidepressants work for PMDD?
Often within the first cycle, faster than for standard depression.
Evidence and sources referenced
- NICE Guideline NG222 — Depression in adults: treatment and management (United Kingdom).
- Royal Australian and New Zealand College of Psychiatrists (RANZCP) — Clinical Practice Guidelines for Mood Disorders.
- NPS MedicineWise — patient and prescriber resources on antidepressants (Australia).
- Royal College of Psychiatrists — patient information on antidepressants.
- TGA and FDA — product information for SSRI and SNRI classes.
- Maudsley Prescribing Guidelines in Psychiatry.
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