The Dark Side of Your Moon: Understanding PMS vs. PMDD

You're picking fights with anyone willing to spar. Your jeans don't fit. You're eating constantly but nothing feels satisfying. Your fuse is basically nonexistent and you know it — you don't even want to be around yourself right now.

Then your family, your partner, your kids ask the question that sends you over the edge: "Are you due for your period?"

The next morning, on day one of your cycle, you wake up feeling like an entirely different person. Lighter. Calmer. The sun actually looks brighter. And now you're apologizing for the week before.

If any of that sounds familiar, you're not alone — and you're not broken. But there's an important question worth asking: is what you're experiencing PMS, or something more significant?

What is PMS?

Premenstrual syndrome is incredibly common, affecting about 1 in 4 people who menstruate (roughly 20–30%).¹ If you have PMS, symptoms show up in the week or so before your period and resolve once bleeding begins. These can include mood swings, irritability, anxiety, bloating, breast tenderness, fatigue, appetite changes, sleep disruption, and brain fog.

To be diagnosed with PMS, you need at least one emotional or physical symptom during the five days before your period, across at least two consecutive cycles.² It's real, it's uncomfortable, and it's worth addressing — but it typically doesn't derail your entire life.

What is PMDD?

Premenstrual dysphoric disorder is the more severe version, affecting about 2–5% of people. The symptoms look similar to PMS, but they're significantly more intense — comparable to clinical depression or anxiety — and crucially, they interfere with your ability to function. We're talking missed work, withdrawn relationships, feeling incapable of managing your daily responsibilities.

PMDD is formally classified as a depressive disorder in the DSM-5,³ which tells you how seriously it's taken clinically. A 2025 study in JAMA Network Open confirmed that premenstrual disorders significantly affect quality of life — and that the impact is often underrecognized and undertreated.⁵ If you find yourself dreading the two weeks before your period because you know what's coming, it's worth exploring whether PMDD might be the right conversation to have with your doctor.

So why does this happen?

It's more complex than just "hormones." Fluctuating estrogen and progesterone affect serotonin — the brain chemical that regulates mood — and some people are more sensitive to those shifts than others. But that's not the whole story. Emerging research published in JAMA Psychiatry found associations between premenstrual disorder symptoms and genetic liability for major psychiatric conditions,⁴ suggesting there may be a heritable component for some people. How you relate to your body, your cycle, and even past trauma can also shape the experience. Researchers are also actively investigating the role of inflammation in monthly physical and emotional changes.

Here's a reframe I love sharing with patients: many people cycle with the moon. The moon isn't always bright and full — there's a dark side. That pre-period week can feel like the dark phase. But when we lean into it rather than fight it, that darkness becomes a space for introspection, creativity, and clarity. Some of the most powerful self-advocacy happens in that window.

What can you do about it?

A lot, actually. Start here:

Regular exercise — especially through your luteal phase (the two weeks before your period) — can raise serotonin levels naturally. Cognitive Behavioral Therapy (CBT) can help you work through the emotional patterns that show up cyclically. Eating a lower-inflammation diet during this time, even when every cell in your body is screaming for chips and chocolate, can reduce symptom severity. Supplements like magnesium, calcium, and chasteberry (Vitex agnus-castus) have shown benefit for some people.

If lifestyle shifts aren't enough, there are medical options too. A luteal-phase SSRI — taken only in the days leading up to your period, then stopped on day one of bleeding — can significantly improve symptoms without the long-term receptor changes that come with daily antidepressant use.¹ Hormonal contraceptives can also stop the luteal phase from occurring altogether, effectively removing the cyclical trigger.²

The bottom line

Emotional and physical changes during your cycle are as natural as the phases of the moon. If those changes are affecting your quality of life, start tracking your symptoms over two to three months — use a journal or an app — and bring that record to your next appointment.

You don't need to suffer every month just because everyone else seems to. Let's talk about it.

— Dr. Erica Kesselman

Sources

1. Ortiz Worthington R, Eastman LM, Alexander JT. Management of Premenstrual Disorders. JAMA. 2026.

2. Biggs WS, Romeu JM, Gaudard T. Premenstrual Syndrome and Premenstrual Dysphoric Disorder: Common Questions and Answers. American Family Physician. 2025.

3. Jeste DV, Lieberman JA, Fassler D, et al. Diagnostic and Statistical Manual of Mental Disorders. American Psychiatric Association; 2022.

4. Jaholkowski P, Shadrin AA, Jangmo A, et al. Associations Between Symptoms of Premenstrual Disorders and Polygenic Liability for Major Psychiatric Disorders. JAMA Psychiatry. 2023.

5. Wang Q, Keijser R, Chen Y, et al. Premenstrual Disorders and Quality of Life in Sweden. JAMA Network Open. 2025.