Borderline Personality Disorder and PMDD: What’s the confusion?

Does your BPD diagnosis ever feel like it’s not quite right?

You might not have considered it before, but what you’re experiencing could actually be premenstrual dysphoric disorder ,(PMDD).

We’ve covered PMDD and its different comorbidities in our previous posts (PMS vs. PMDD, Severe PMS & PMDD, PMDD symptoms), but to refresh your memory: PMDD is a severe mood disorder that follows your menstrual cycle. Symptoms like irritability, intense mood swings, fatigue, and pain ramp up during the luteal phase (the time between ovulation and menstruation), often making your daily life feel unmanageable.

You might be wondering how a hormone-based disorder like PMDD can get confused with borderline personality disorder (BPD). Let’s look at why this misdiagnosis is surprisingly common - and how tracking your symptoms could be the key to finding the right support.

An innocent oversight

There’s one simple detail that often gets missed during diagnosis: symptom timing.

PMDD symptoms follow a pattern; flaring up during the luteal phase and easing off once your period starts.

BPD, on the other hand, is a chronic condition without clear breaks or recovery windows.

As straightforward as it sounds, asking when symptoms occur can make a big difference in diagnosis. But if we’re being honest, awareness of PMDD is still limited. So when you report mood swings, irritability, or emotional sensitivity, many clinicians may not think to connect the dots with the menstrual cycle and ask about when these symptoms occur.

So why should we look at symptom timing as a factor? Because BPD and PMDD actually share a number of major characteristics (Peters, 2020):

· Intense mood swings

· Irritability

· Sensitivity to rejection

Therefore timing might be the only obvious thing to tell the two disorders apart.

Hormones and BPD

If what we’ve talked about resonates with you, there might be another complication to consider: BPD symptoms can get worse before your period, potentially making it seem cyclical like PMDD.

In fact, a study found around 6 out of 10 women with BPD reported more intense symptoms in the days leading up to their period. This included spikes in anger, anxiety, and rejection sensitivity. The likely culprit? The sharp drop in progesterone right before menstruation (Eisenlohr-Moul, 2019).

So even if you tell your clinician that your symptoms worsen before your period, a diagnosis of BPD might still seem to “fit”- at least on the surface. As nearly 75% of people diagnosed with BPD are women, it’s an understandable assumption.

But that doesn’t mean it’s the right fit

where do you go from here?

Symptom relief

It turns out that tracking when your symptoms worsen isn’t enough - what really matters is when (or if) they go away.

Both PMDD and BPD can feel more intense before your period. But only PMDD tends to fully resolve once your period starts, with relief typically lasting through to ovulation.

Looking back at the study we picked out earlier (Eisenlohr-Moul, 2019), whilst the participants reported their symptoms got worse premenstrually, none of them met the criteria for PMDD. Why? Because their symptoms didn’t disappear after their period - they simply dropped back to their usual baseline of ongoing low mood.

In other words, it’s not just about whether your symptoms are cyclically worsening. It’s whether they resolve cyclically too.

The importance of correct diagnosis

If you’ve been diagnosed with BPD but feel that PMDD could be the root cause of your symptoms, you might be wondering - does the label really matter?

In short, yes - because getting it right means finding the right care.

BPD is usually treated with talk therapy - most often Dialectical Behaviour Therapy (DBT). DBT is designed to help people manage intense emotions and shift long-standing patterns, especially for those with a history of emotional invalidation or trauma. Medications like mood stabilizers are sometimes added.

PMDD, on the other hand, is treated very differently. Mainstream options include cognitive behavioural therapy (CBT), antidepressants that are sometimes taken only during the luteal phase, hormonal treatments like the combined contraceptive pill, and emerging non-hormonal approaches like neuromodulation, which target brain circuits involved in mood and pain regulation..

So, if you’re receiving treatment for BPD when in fact the reason it feels like your life topples over once a month is because of PMDD, you’re probably not getting the relief you’re looking for.

Tracking your cycle is key

Spotting the rhythm to your symptoms might be the answer to working out what’s going on. A simple, accessible method? Cycle tracking.

Cycle tracking with Samphire is more than just a calendar of when your period is due. It helps you monitor the severity of your mood, pain, energy and many more factors that have been making your life so difficult.

If the struggles that paralyze you rear their head in your luteal phase, then seemingly disappear, you could very well have PMDD.

To help ease your symptoms, Nettle™ offers non-invasive brain stimulation that gently supports emotional regulation during the luteal phase by mimicking your brain in the follicular phase, helping you stay grounded when it matters most.

Understanding the pattern of your symptoms isn’t just helpful to finally figure out what’s causing your struggle, it’s the first step in getting your life back on track.