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Episode 20: AuDHD Explained — Misdiagnosis, BPD & Mental Health in Late-Diagnosed Adults

In this episode of the AuDHD Psych Podcast, clinical psychologist Aaron Howearth and co-host Dan unpack why mental health diagnosis is so complex for AuDHDers, and why so many of us collect a stack of labels — depression, generalised anxiety, borderline personality disorder, bipolar, treatment-resistant depression — before Autism and ADHD are ever properly considered. Drawing on clinical work, lived experience, and the qualitative research literature, Aaron explains how diagnostic overshadowing happens, why internalising presentations are most at risk of misdiagnosis, and what genuinely neurodiversity-affirming assessment looks like in practice.

Aaron and Dan work through the mechanics of overshadowing — how a clinician's existing diagnostic lens quietly re-explains every new symptom and closes the door on alternative formulations — and the elevated mental health risks that ride alongside AuDHD, including anxiety, depression, self-harm and suicidality. They examine why biological females and internalising males are disproportionately mislabelled with borderline personality disorder when emotional impulsivity, rejection sensitivity and rigid thought patterns are actually expressions of an undiagnosed AuDHD profile. They then move into the practical: how to script questions for your clinician without it landing as an attack, why differential diagnosis and formulation are the antidote to overshadowing, and how late diagnosis reframes self-concept from "bad person, not trying hard enough" to environment-fit. Throughout, the conversation returns to the affirming reframe — difficulties arise from the mismatch between who you are and what the environment expects, not from a defective self.

Key Themes & Takeaways

• Co-occurrence Is the Rule, Not the Exception – Around 40% of autistic people have a co-occurring mental health condition, ADHDers are similarly elevated, and AuDHDers sit at higher risk again for anxiety, depression, self-harm and suicidality.
• Diagnostic Overshadowing Defined – Once a clinician holds one diagnostic lens, new symptoms get re-explained through it, and alternative formulations stop being considered.
• The Observation Fallacy – Clinicians can only diagnose what they know to look for; if AuDHD isn't on the radar, the symptoms get mapped to whatever lens is familiar.
• BPD as the Classic Misdiagnosis – Emotional impulsivity, rejection sensitivity, identity disturbance and rigid thought can all be AuDHD expressions, particularly in biological females and internalisers whose presentations don't match the externalising male stereotype that built the diagnostic criteria.
• 1 in 5 Autistic Adults Report Overshadowing – Lived experience and self-report research show roughly 20% of autistic adults have experienced misdiagnosis or missed diagnosis tied to overshadowing.
• Treatment-Resistant Doesn't Mean Broken – When treatment plans target the wrong formulation, "not responding" is a systems failure, not a character flaw or proof of imposter syndrome.
• Differential Diagnosis & Formulation – Good assessment ticks the diagnostic boxes and excludes confounds, situating symptoms inside developmental history, sensory profile, trauma, family history and cognitive profile.
• Neurodiversity-Affirming Assessment – Goes beyond awareness to actively consider AuDHD interactions, masking effects, and the cognitive and sensory differences that shape presentation and treatment.
• Scripting for Appointments – Lines like "I'm wondering how you came to that conclusion — do you have a formulation that led to the treatment plan?" make hard conversations doable without lan