The Diagnostic Gap: When Your Brain Doesn't Fit into a Medical Box

The Long Wait for a Question Mark

For those of us who have spent a lifetime feeling slightly out of step with the world, the decision to seek a formal neurodivergent assessment is rarely impulsive. It is a choice, often preceded by years of private research and a growing, quiet hope. We sit on waiting lists for months, sometimes years, tethered to the belief that at the end of this journey lies a definitive name—a key that will finally unlock the "why" behind our experiences. We anticipate a period, an ending to the sentence of our uncertainty. But for many, the process concludes not with a label, but with a lingering, frustrating question mark. This is the reality of the "diagnostic gap," where the brain’s complexity exceeds the clinical world’s narrowest definitions.

The Myth of the Guaranteed Diagnosis

If you follow mainstream media narratives, you would be forgiven for believing that every referral inevitably leads to a diagnosis. The current discourse suggests a conveyor belt system: you wait, you’re seen, and you’re handed a folder labelled ADHD or Autism.

The reality I encountered, and one that many share is far more messy. We fill out exhaustive questionnaires, relive our most vulnerable moments for strangers, and attend clinical interviews, only to be told we don’t quite fit the criteria. The assumption that "referral equals diagnosis" is a myth that ignores a growing population of people left in limbo, having completed the gauntlet of the medical system only to remain officially "unlabelled."

The Language Clash: "Symptoms" vs. Identity

My own journey hit its first snag before the assessments even began. I was caught off guard when my GP rang me back surprisingly quickly after I submitted my initial forms. The conversation was brief, but the terminology was jarring. I was asked to list my "symptoms."

To a clinician, this is standard procedure. To someone viewing their brain through a neurodiversity-affirming lens, it felt like a fundamental misunderstanding. "Symptoms" imply a pathology—a disease to be cured or a malfunction to be corrected. But my brain isn’t a broken version of a "normal" one; it is simply my brain.

"Symptoms to me suggest disease, an issue or something that must be fixed. Neurodivergent conditions are not that – they are intrinsically part of who we are."

This clash of language is more than just semantics; it sets the tone for a system that looks for deficits rather than understanding a person's core identity.

The Referral Loop: A "Messy Profile" in a World of Neat Boxes

The medical model loves a neat box. It relies on the DSM-5’s strict thresholds, but human neurodivergence is rarely so tidy. I entered the system already holding a dyslexia diagnosis, but I knew it didn’t cover the full scope of my experience—the intense Rejection Sensitivity Dysphoria (RSD) and the specific sensory sensitivities I have around touch.

What followed was a masterclass in clinical irony. My ADHD clinician, after observing my traits, suggested that my challenges might actually be Autism and recommended an assessment there. Three months later, during my Autism assessment, the clinicians spent an hour talking to me before disappearing for ten minutes to deliberate on my "verdict." When they returned to the screen, the diagnosis I was craving slipped away. They told me I didn't meet the threshold for Autism. Instead, they suggested that what I had described sounded remarkably like ADHD—the very diagnosis I had already been told I didn't qualify for.

I found myself caught in a circular finger-pointing exercise. I have "too much" for my dyslexia label to explain, but not "enough" of any one thing to satisfy the clinical gatekeepers. I have a "messy profile" in a world that only recognises neat ones.

The Impossible Memory Test: Why the Childhood Lens Fails Adults

One of the most significant barriers for adults (particularly for women) is the medical system's obsession with the childhood lens. To receive an ADHD or Autism diagnosis, one must provide concrete evidence of traits presenting in early childhood. During my assessment, I found myself racking my brain for specific examples from decades ago, trying to make sense of questions that felt fundamentally illogical. I was asked: "Do you miss people after a long time?" My internal response was a flurry of confusion: Define "long time." What does "miss" look like in this context?

For many of us, the childhood lens is a wall. We may have been expert "maskers," blending in so well that there is no external record of our internal struggle. Or, quite simply, we cannot remember the minutiae of our cognitive processes from thirty years ago. When a diagnosis hinges on the clarity of a distant memory, the system effectively fails the very adults it is supposed to help.

Reframing Validation: The Professional’s Paradox

After hours of questionnaires and clinical scrutiny, the "verdict" I received was a suggestion that I try coaching. There is a poignant irony here: I as a recently trained coach, my passion and aim is to help others navigate these very challenges. I found myself in the bizarre position of being unable to "help myself" through the medical system, yet being told that the help I provide to others was exactly what I needed.

This experience forced me to question the value of external validation. If my own research has already identified my challenges, do I really need a doctor’s permission to claim my identity? For those of us in the diagnostic gap, self-identification becomes a pragmatic necessity. Whether I choose to call myself "neurodivergent" or self-diagnose as AuDHD, I am choosing to trust my own internal map over a medical system that can’t decide which box I belong in.

Conclusion: Beyond the Label

The current diagnostic system often fails to capture the "lost middle ground"—those of us whose traits are significant and life-altering, yet don't meet an arbitrary clinical threshold. We are more than the sum of our "failed" assessments.

If the medical boxes aren't big enough to hold our experiences, is it time we stop trying to fit into them and start trusting our own internal maps?

FAQs

1. What is the “diagnostic gap” in neurodivergent assessments?

The diagnostic gap refers to the experience of going through formal ADHD or Autism assessments and emerging without a diagnosis, despite having significant traits. It describes the space where a person’s lived reality doesn’t fit neatly into the narrow clinical thresholds used by diagnostic systems. Many people wait months or years for assessments only to be told they don’t meet criteria, leaving them in a state of uncertainty rather than clarity.

2. Why doesn’t every referral for ADHD or Autism lead to a diagnosis?

There is a common misconception that being referred automatically results in a diagnosis, but the reality is far more complex. Assessments rely on strict DSM‑5 criteria, clinician interpretation, and often incomplete childhood evidence. Many people fall into a “clinical limbo” where their traits are real and impactful but don’t align neatly with diagnostic checklists, meaning they remain officially “unlabelled.”

3. Why can clinical language like “symptoms” feel invalidating to neurodivergent adults?

Terms such as “symptoms” imply illness, pathology, or something that needs to be fixed. For people who view neurodivergence as an identity rather than a disorder, this language can feel jarring and misaligned. It frames natural cognitive differences as deficits, setting a tone that prioritises what is “wrong” rather than understanding the person’s lived experience.

4. Why is the childhood lens a barrier for adults seeking ADHD or Autism diagnosis?

Adults — especially women and lifelong maskers — often struggle to provide detailed childhood examples required for diagnosis. Many cannot recall specific behaviours from decades ago, and external records may not exist because they blended in or compensated. When diagnostic approval depends heavily on childhood evidence, the system inadvertently excludes the very adults it aims to support.