PMS or PMDD?
How they differ
By Ben Jonas Goedeke · 3 min read · checked against its sources · updated 10 Oct 2026
Most people who have periods notice something in the days before: a shorter temper, sore breasts, a low afternoon. That is premenstrual syndrome, or PMS. It is common and usually manageable.
Premenstrual dysphoric disorder, PMDD, is different in degree. The mood symptoms are strong enough to get in the way of work, relationships and ordinary days. People describe feeling like a different person for a week or two, and then like themselves again once their period starts.
The timing is the clue
What the two share is timing. Symptoms show up in the second half of the cycle, after ovulation, and ease within a few days of bleeding. If you feel the same all month, something else may be going on, and that is worth raising with a doctor too.
How a doctor tells them apart
A PMDD diagnosis looks for at least five symptoms in the week before your period, at least one of them about mood, such as irritability, sadness, anxiety or mood swings. They ease within a few days of bleeding and are mild or gone in the week after. And they have to show up in daily notes over at least two cycles, not only in memory.
Only a doctor can tell you
No app can diagnose PMDD, and Tideline does not try to. What it can do is keep the record a doctor needs: what you felt, how strongly, and on which day of your cycle.
Keep the record your doctor needs. Tideline is a period and mood tracker for iPhone: write one sentence a day, and after two cycles it puts the week before your period next to the week after it starts. Free to track, no account.
Get Tideline on the App Store
Keep reading
Sources
- NHS: PMS (premenstrual syndrome)
- US Office on Women’s Health: Premenstrual syndrome (PMS)
- ACOG: Premenstrual Syndrome (PMS)
- IAPMD: What is PMDD?
- IAPMD: Steps to diagnosis
- MedlinePlus (US National Library of Medicine): Premenstrual dysphoric disorder