A particular kind of referral has become familiar to me over the past decade. A woman in her thirties or forties arrives with a history with mental health struggles. Somewhere in that file is a diagnosis of borderline personality disorder, often made years earlier, sometimes after a single crisis presentation. She has been told she is “emotionally unstable,” that her relationships are the problem, that she is difficult to treat. And yet, when I take a careful developmental history, a different picture keeps emerging: sensory sensitivities since early childhood, a lifelong sense of being subtly out of step socially, exhausting efforts to appear “normal,” intense and narrow interests. On formal assessment, she meets criteria for autism. The borderline label, it turns out, may have been describing the surface of something it never named.
| Feature | Autism | Borderline PD | Complex PTSD |
|---|---|---|---|
| Onset / origin | Lifelong; present from early childhood | Adolescence / early adulthood | Follows chronic, often interpersonal trauma |
| Sense of self | Stable, but eroded by masking | Genuinely unstable, shifts with context | Stable but persistently negative |
| Relationships | Wants connection; difficulty reading cues; depleting | Intense, volatile; idealisation–devaluation; abandonment fear | Avoidant, mistrustful, hypervigilant |
| Emotional dysregulation | Neurological; overload/meltdown, sensory-driven | Reactive to interpersonal triggers; rapid shifts | Trauma-driven; triggered by reminders |
| Social difficulty | Different social communication and processing | Altered social cognition tied to relational fears | Withdrawal from mistrust and threat |
| Sensory / sameness | Sensitivities, routine, repetitive behaviour (lifelong) | Not characteristic | Not characteristic (hyperarousal differs) |
| Trauma history | May or may not be present | May be present | Required |
| Helpful measures | CAT-Q, AQ, RAADS-R, CATI | MSI-BPD, BSL-23 | ITQ, LEC-5, ACE-Q |
I want to take the question in the title seriously, because it is being asked loudly in clinical and autistic communities right now, and because the answer matters enormously for how we treat people. My view, after reading the literature, is this: yes, a meaningful proportion of women historically diagnosed with BPD were probably autistic, or autistic and traumatised — but the relationship is genuinely complicated, the conditions really do co-occur, and the fashionable over-correction (“BPD isn’t real, it’s all autism”) is its own diagnostic error. Let me work through why.
The first thing to establish is that the symptomatic overlap between autism and BPD is substantial and well-documented, not a fringe claim. Both can present with emotional dysregulation, unstable or intense interpersonal relationships, identity confusion, impulsivity, self-harm, and chronic feelings of emptiness. When you are working from a symptom checklist rather than a developmental formulation, the two can look remarkably alike.
The empirical work bears this out. In the largest study of its kind, Dudas and colleagues (2017) administered the Autism Spectrum Quotient to over 600 autistic adults, a group with BPD, a comorbid group, and more than 2,000 controls, and found that people with BPD showed elevated autistic traits relative to controls — sitting, in trait terms, partway between neurotypical and autistic groups. A subsequent review by Dell’Osso and colleagues (2023) synthesised the comorbidity data and reported figures that should give any diagnostician pause: across studies, around 12% of autistic adults met criteria for BPD; among referred autistic adults, comorbid BPD was roughly three times more common in women than men (about 15% versus 5%); and, looking from the other direction, close to half of women diagnosed with BPD in one sample scored above the autism cut-off on the AQ. These are screening-level findings rather than confirmed diagnoses, and trait elevation is not the same as a categorical condition — but the signal is consistent and it points the same way.
There is also a phenomenological dimension that the statistics miss. Tamilson, Eccles and Shaw (2025) interviewed autistic adults who had previously been diagnosed with borderline or emotionally unstable personality disorder. Almost all described autistic differences reaching back into childhood that had gone unrecognised, and most experienced the borderline diagnosis as a misattribution — a label applied to autistic distress and overwhelm rather than to a personality pathology. Whatever we make of self-report, the lived account is strikingly uniform.
The reason this question centres on women is that autism in girls and women was, for decades, systematically under-recognised. In my university days, it was a so-called known “fact” that the prevalence of autism in women was tiny. How our understanding has changed in the last decade, especially now that we understand autistic camouflaging so much better.
Historically, the often-quoted male-to-female ratio of around 4:1 is itself partly an artefact of that bias; Loomes, Hull and Mandy (2017), in their meta-analysis, found a pooled odds ratio of 4.2 but concluded that the true ratio is closer to 3:1, with girls who meet criteria disproportionately missed by services. The “female autism phenotype” tends to involve subtler social difficulties, fewer obviously unusual interests (or interests that are socially camouflaged, such as animals, fiction, or psychology rather than timetables), and, crucially, sophisticated camouflaging: the conscious and unconscious masking of autistic traits to pass as neurotypical. A girl who has spent her childhood studying how other people behave and copying it will not look autistic to a clinician using a male-normed template. She will look like someone who is struggling socially and emotionally for reasons that need another name.
Running alongside this is a well-documented gender bias in the other direction: clinicians are more inclined to diagnose BPD in women. McQuaid, Strang and Jack (2024), in a thoughtful conceptual analysis, argue that these two biases compound, a reluctance to see autism in women and a readiness to see borderline personality in them. so that the autistic woman presenting in distress is funnelled towards a BPD diagnosis almost by default. The features most prone to miscategorisation are exactly the ones the two conditions share: meltdowns read as affective instability, social exhaustion read as relationship dysfunction, and a fragmented sense of self that, in the autistic woman, often reflects a lifetime of masking rather than the identity disturbance of BPD.
If this were only a two-way problem, it would be hard enough. But there is a third element that I think is essential, and it is the reason I have framed this article around three conditions rather than two: complex PTSD.
Autistic people, and autistic women in particular, are exposed to more trauma than their non-autistic peers. The social vulnerability that comes with misreading others’ intentions, the experience of being bullied and excluded, and the sheer cumulative stress of navigating a world not built for you all raise the risk. The consequences show up in the trauma data: Rumball, Happé and Grey (2020) found that more than 40% of trauma-exposed autistic adults showed symptoms consistent with probable PTSD, and that a broader range of life events functioned as traumatic for autistic people than the standard criteria anticipate.
Now consider what complex PTSD looks like; the ICD-11 construct of PTSD plus “disturbances in self-organisation”: affect dysregulation, a persistently negative self-concept, and difficulties in relationships. Those three features overlap heavily with both BPD and the lived experience of being an unsupported autistic woman. So we have three conditions, autism, BPD, and CPTSD, that can converge on a near-identical surface presentation of emotional dysregulation, relational difficulty, and a damaged sense of self. In many of the women I assess, the honest formulation is not “which one of these is it?” but “an autistic woman, missed in childhood, who has been chronically traumatised partly because she was autistic and unsupported, and who has accumulated a borderline label along the way.” Pulling those threads apart is the actual clinical work.
Differentiation is possible, but it rests on developmental history and mechanism rather than on a cross-sectional symptom count. These are the distinctions I lean on most.
Time course and origin. Autism is lifelong and present from early development; its traits predate any crisis. BPD typically consolidates in adolescence or early adulthood. CPTSD, by definition, follows chronic trauma. If the sensory sensitivities, social differences, and need for sameness were there at age five — long before any relational trauma or identity crisis, autism belongs in the preliminary formulation regardless of what else is going on.
Sense of self. This is the single most useful discriminator in my experience, and the cross-sectional evidence agrees: in a study of women and people assigned female at birth, identity disruption was the feature that most strongly distinguished those with BPD from autistic participants, while the autistic group scored higher on sensory processing, preference for sameness, and repetitive motor behaviour (Barnicot et al., 2026). In BPD, the sense of self is genuinely unstable — it shifts with context and relationships. In autism, the self is often quite stable and consistent; what looks like identity confusion is usually the exhaustion and self-alienation of long-term masking (“I don’t know who I am because I’ve spent my life pretending to be someone else”). In CPTSD, the self-concept is stably negative rather than unstable.
The shape of relationships. BPD relationships tend to be intense and volatile, oscillating between idealisation and devaluation, organised around a terror of abandonment. Autistic relationship difficulties more often reflect genuinely not reading social cues, or withdrawing because interaction is depleting. CPTSD pushes towards avoidance and mistrust. The autistic woman frequently wants closeness but finds it bewildering; that is a different thing from the abandonment-driven turbulence of BPD.
Sensory and repetitive features. Sensory sensitivities, a strong preference for routine and sameness, and repetitive behaviours weight heavily towards autism and are not part of the BPD or CPTSD picture. When present and lifelong, they are among the most specific signals we have.
Because the surface presentations converge, I rely on structured measurement across all three domains rather than trusting clinical impression alone — and I am candid that impression is precisely what got many of these women mislabelled in the first place.
For autism, I think the Camouflaging Autistic Traits Questionnaire (CAT-Q) is close to indispensable in this population. It is the instrument most likely to surface the very mechanism — masking — that explains why an autistic woman went unrecognised, and a high camouflaging score in a woman with a “borderline” history is a strong prompt to assess for autism properly.
I pair it with a trait measure such as the RAADS-R or the Comprehensive Autistic Trait Inventory (CATI), always read against a developmental history rather than in isolation. The CATI is normed against women specifically, and was developed with women in mind, which makes it my peak over more traditional measures such as the Autism Spectrum Quotient (AQ).
For the personality and trauma side, the McLean Screening Instrument for BPD (MSI-BPD) and the Borderline Symptom List (BSL-23) quantify borderline features, while the International Trauma Questionnaire (ITQ) was purpose-built to separate PTSD from complex PTSD and is the tool I reach for when trauma is in the frame. Documenting the trauma history itself with the Life Events Checklist (LEC-5) and the Adverse Childhood Experiences Questionnaire (ACE-Q) matters, because in this group trauma is often present and unaddressed. I’ve written more about that particular differential in our guide to BPD versus complex PTSD, and about the broader reasoning in the pillar on differential diagnosis.
My honest answer is a qualified yes. I have personally made this mistake.
I think the historical under-recognition of autism in women, compounded by a gender bias toward diagnosing BPD, produced a cohort of women carrying a borderline label that did not capture what was actually going on — and for some of them, autism (frequently with a layer of complex trauma) is the better-fitting formulation. The relief and self-understanding that a correct autism diagnosis brings these women, often in mid-life, is one of the more moving things I see in practice.
But I want to resist two temptations. The first is to swing to the opposite extreme and treat BPD as a fiction. It is not; it is a valid, well-validated construct, and some women referred with the question “could this be autism?” do have borderline personality disorder, with or without co-occurring autism. The second temptation is to treat these as either/or. The evidence is clear that autism and BPD genuinely co-occur, and that comorbid presentations carry higher risk — including more frequent suicide attempts and lower functioning — which makes getting the full picture, rather than picking a single winner, the thing that actually protects people.
The cost of error runs in both directions. Misread an autistic woman as borderline and you may subject her to treatment that pathologises her neurology, misses her sensory and communication needs, and adds to the trauma. Miss genuine BPD or CPTSD by attributing everything to autism and you withhold trauma-focused or DBT-informed care that could change her life. The discipline of differential diagnosis — developmental history, structured measurement across all three domains, and a willingness to hold more than one diagnosis at once — is what keeps us from either failure. That, ultimately, is the case for doing this work properly rather than quickly.
Dr Ben Buchanan is a clinical psychologist and the founder of NovoPsych. This article is general clinical information, not a substitute for individual assessment.
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Barnicot, K., Thompson, E., Turner, S., Mandy, W., McCabe, R., Stark, E., & Parker, J. (2026). Overlapping and differentiating clinical features of autism and borderline personality disorder in women and people assigned female at birth: A cross-sectional study. Autism. Advance online publication. https://doi.org/10.1177/13623613261431309
Dell'Osso, L., Cremone, I. M., Nardi, B., Tognini, V., Castellani, L., Perrone, P., Amatori, G., & Carpita, B. (2023). Comorbidity and overlaps between autism spectrum and borderline personality disorder: State of the art. Brain Sciences, 13(6), 862. https://doi.org/10.3390/brainsci13060862
Dudas, R. B., Lovejoy, C., Cassidy, S., Allison, C., Smith, P., & Baron-Cohen, S. (2017). The overlap between autistic spectrum conditions and borderline personality disorder. PLOS ONE, 12(9), e0184447. https://doi.org/10.1371/journal.pone.0184447
Loomes, R., Hull, L., & Mandy, W. P. L. (2017). What is the male-to-female ratio in autism spectrum disorder? A systematic review and meta-analysis. Journal of the American Academy of Child & Adolescent Psychiatry, 56(6), 466–474. https://doi.org/10.1016/j.jaac.2017.03.013
McQuaid, G. A., Strang, J. F., & Jack, A. (2024). Borderline personality as a factor in late, missed, and mis-diagnosis in autistic girls and women: A conceptual analysis. Autism in Adulthood, 6(4), 401–427. https://doi.org/10.1089/aut.2023.0034
Rumball, F., Happé, F., & Grey, N. (2020). Experience of trauma and PTSD symptoms in autistic adults: Risk of PTSD development following DSM-5 and non-DSM-5 traumatic life events. Autism Research, 13(12), 2122–2132. https://doi.org/10.1002/aur.2306
Tamilson, B., Eccles, J. A., & Shaw, S. C. K. (2025). The experiences of autistic adults who were previously diagnosed with borderline or emotionally unstable personality disorder: A phenomenological study. Autism, 29(4), 1056–1069. https://doi.org/10.1177/13623613241276073
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