Borderline personality disorder (BPD) is the single most common misdiagnosis given to people who actually have dissociative identity disorder (DID), because both conditions involve a disturbed sense of identity, self-harm and relationships that swing between extremes. They are genuinely different conditions with different treatments, and telling them apart reliably takes a full clinical assessment, not a checklist.
Our DID overview gives this comparison a single table row. This article stays with it: why the mix-up happens so often, whether someone can actually have both, and what a clinician is really checking for when they try to tell them apart.
Why is DID so often diagnosed as BPD
The overlap is real, not carelessness on a clinician’s part. Identity disturbance, chronic self-harm, a history of severe early adversity and relationships that lurch between idealising someone and being furious with them show up in both conditions, and a first assessment rarely has time to establish which one is actually producing the pattern.
What tends not to get asked about is the thing that would separate them. Most standard assessments probe mood, relationships and impulsivity in detail and say almost nothing about memory gaps or switching between states, so the feature that points toward DID is frequently the one nobody raised. A study using a validated measure of identity alteration found that people who were less aware of their own identity shifts were more likely to be steered toward a BPD diagnosis instead, which is close to the mechanism at work here: the sign that would redirect the assessment is the one that stayed unasked. [sar-2017-identity-alteration]
The confusion also runs the other way to a degree, which is worth being honest about. Korzekwa and colleagues measured the full range of dissociative experience directly in a group of people with BPD, rather than assuming its absence, and found depersonalisation, derealisation and identity confusion to be common, with a meaningful minority also meeting criteria for a dissociative disorder in their own right. [korzekwa-2009-dissociation-bpd] Some genuine dissociation inside BPD is part of why the two conditions get tangled together, not only a story about missed DID.
Can you have both DID and BPD
Yes, and it is common enough that a good assessment checks for both rather than treating one diagnosis as ruling out the other. Ross and colleagues interviewed inpatients in a trauma treatment programme and found that people who met criteria for both conditions were the most symptomatic and the most heavily traumatised group, more so than people who met criteria for either one alone. [ross-2014-cooccurrence] That is not two labels stacked for the sake of it. It reads as one severe presentation that happens to satisfy two sets of diagnostic criteria at once.
In practice this means a diagnosis of one should not close the door on asking about the other, particularly where treatment for the first diagnosis has not worked as expected. It also means neither label should be assumed automatically because the other one is present: the two are correlated in the research, not identical.
No screener on this site, or anywhere reputable, is built to sort this out from a list of questions. The self-assessment hub covers anxiety, depression, stress, sleep, burnout, self-esteem and loneliness, none of which distinguishes DID from BPD or diagnoses either one, and nothing here should be read as a stand-in for the structured clinical interviews that actually can.
What actually tells them apart
Two features carry most of the real diagnostic weight: whether there are genuinely separated identity states, and whether there is recurrent amnesia between them. BPD does not require either, however severe the identity disturbance feels day to day.
| Feature | Borderline personality disorder | Dissociative identity disorder |
|---|---|---|
| Sense of self | One self, experienced as chronically unstable or empty, especially around relationships | Two or more distinct identity states, each fairly consistent in itself, that take over at different times |
| Memory | No true amnesia for one’s own actions; memory can feel patchy under extreme distress | Recurrent gaps for everyday events, personal information, or actions taken while in another state |
| What sets off a shift | Perceived rejection, criticism or fear of being abandoned | Often stress or trauma reminders, but the switch itself is not primarily about the person in front of them |
| How long it lasts | Emotional storms commonly run hours to days, without a change in who is present | Switching can be abrupt, and different states can be present for varying stretches of time |
| When it starts | Adolescence or early adulthood; can ease significantly with age and treatment | Rooted in severe childhood trauma; the separated states are usually present long before anyone identifies them |
| First-line treatment | Dialectical behaviour therapy or another specific psychotherapy for BPD | Phased, trauma-focused therapy, stabilisation before any processing of traumatic memory |
The amnesia row is the one that does the most work in an actual assessment. Losing hours, finding evidence of things done with no memory of doing them, or being told about conversations that left no trace is not part of BPD’s own diagnostic picture, even though the identity disturbance criterion sounds like it could cover the same ground. Brand and colleagues, reviewing the evidence against the popular myths about DID, found the conflation of the two conditions to be one of the more persistent ones, precisely because casual observation of intense identity disturbance is not the same test as asking specifically about switching and lost time. [brand-2016-separating]
Why the right diagnosis actually matters
It matters because the two front-line treatments barely overlap. Dialectical behaviour therapy, the best-established treatment for BPD, is built around emotion regulation, distress tolerance and interpersonal skills; it was not designed to address dissociative amnesia or coordination between separated identity states, and a person with genuine DID can go through it without the part of their difficulty that actually needs treating ever being named. Trauma-focused, phased treatment for DID, in turn, starts with stabilisation for a reason: processing traumatic memory before that groundwork is done reliably makes people worse.
A wrong diagnosis, in either direction, tends to mean years spent on a treatment aimed at the wrong target rather than a treatment that simply failed. That is expensive in time no one gets back, which is the whole reason getting the distinction right is worth the extra questions an assessment has to ask.
Which pattern sounds more familiar?
This is a reflection prompt, not a test for either condition. Answer about your own experience and treat the result as a reason to raise this with a professional, never as a verdict on which diagnosis fits.
0 of 5 ticked
This many ticked is a strong reason to ask directly for an assessment that includes dissociative symptoms, especially if you already carry one of these diagnoses and treatment has not helped. Making that request is the next step, not this list.
A cluster of these is exactly what should prompt a request for an assessment that specifically covers dissociation, not only mood and relationships. Only a clinician who asks about both directly can tell what is actually happening.
Even one item like this is worth mentioning to a professional in your own words. These patterns show up across several conditions, and the point of naming them is to get a proper assessment, not to score yourself against either diagnosis.
No screener on this site is built to distinguish DID from BPD or diagnose either condition; only a clinical assessment can. The hub lists what we do cover.
When to seek help
Speak to a doctor or a mental health professional if you recognise memory gaps you cannot account for, a sense of self that separates into distinct states rather than merely feeling unstable, or if you have been treated for one of these conditions without real improvement. Ask specifically for an assessment that covers dissociation, since standard assessments generally do not, and say so plainly even though describing lost time out loud can feel like the hardest part.
This applies just as much if it is someone close to you who carries one of these diagnoses and the picture has never quite fitted. Raising the question with their clinician, or encouraging them to, is a reasonable next step rather than second-guessing a diagnosis from the outside.
Contact your local emergency services or a crisis helpline if you feel unsafe or are at risk of harming yourself.
How MyFreud can help
Neither of these conditions is something to work out alone, and MyFreud is not a diagnostic tool for either one. What daily tracking can do is make patterns visible that are genuinely hard to hold in memory, gaps in time, what a low mood was actually about, how long a shift in relationships or sense of self actually lasted, which is exactly the kind of detail an assessment for either condition depends on. Live coaching sessions give you a place to put that account into words before an appointment, and the notepad is where the details go as you notice them, rather than trying to reconstruct them all at once under pressure.
Download MyFreud and start today: App Store or Google Play.