Mental Illness, Diagnosis and the Limits of Classification
A reflection on mental illness, classification systems, and the limits of labels.
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| A diagnosis may describe a pattern, but it can never describe the whole person. |
What We Call Ill
A diagnosis of mental illness is not a natural entity waiting to be discovered. It is a classification — a framework developed by researchers and practitioners to describe patterns of symptoms and impairment. And like any framework, it can change.
In 1980, the diagnosis “anxiety neurosis” was abandoned and replaced with “panic disorder” and “generalised anxiety disorder.” The experiences people had did not suddenly disappear. The way those experiences were classified changed.
This is not necessarily a flaw. It is a reminder that scientific understanding develops over time. A diagnosis is not a complete truth about a person. It is a framework for describing a particular pattern — and frameworks can be revised.
What Mental Illness Is and What It Is Not
A mental illness is not simply “feeling bad.” It is a clinically relevant pattern of symptoms associated with significant distress and/or impairment in daily functioning. Not every sadness is depression. Not every worry is anxiety. Not every unusual behaviour is pathology.
The distinction is guided by diagnostic criteria — internationally developed, clinically informed, and continually reviewed. These criteria exist within classification systems. And those systems are not the same as the person being described.
How We Got Here
The understanding of mental illness has shifted across centuries, and those shifts are not just academic. They influence how people understand and respond to psychological suffering.
| Era | View | Consequence |
|---|---|---|
| Antiquity | Imbalance of body fluids | Natural explanation — an early attempt to explain mental disturbance. |
| Middle Ages | Possession, demons | Exclusion and inhumane treatment. |
| 18th/19th century | Medical condition | Pinel demands dignified treatment. Psychiatric clinics develop. |
| Late 19th century | Psychoanalysis | Unconscious processes enter psychological explanation. |
| Early 20th century | Behaviourism | Learning and conditioning become central explanations of behaviour. |
| 1960–1980 | Cognitive behavioural approaches | Thoughts and behaviour become central targets of psychological intervention. |
| Post-1990 | Acceptance, mindfulness, emotion-focused approaches | Self-regulation, acceptance, and personal resources gain greater attention. |
Each shift was not just a change in theory. It was a change in how we see people — and therefore how we respond to them.
The Triadic System — A Historical Map
Before modern classification, there was the triadic system — a three-part model that grouped mental disorders according to their assumed cause:
| Category | Assumed Cause | Examples |
|---|---|---|
| Exogenous | Physical, identifiable cause | Neurological illness, substance-induced disorders, dementia. |
| Endogenous | “From within” — no external cause identifiable | Schizophrenia, bipolar disorders. |
| Psychoreactive | Reactive to psychological stress | Anxiety, depression, personality disorders, eating disorders, addiction. |
The triadic system is outdated. It is useful here not because it remains clinically current, but because it shows how classification systems reflect the assumptions of their time.
The triadic model assumed a relatively clean separation between “physical,” “from within,” and “reactive.” Contemporary approaches generally recognise that mental disorders can involve multiple interacting factors. The biopsychosocial model offers a more integrated way of understanding this complexity.
ICD and DSM — Two Systems, One Goal
Today, the ICD and DSM are two major classification systems used in mental health. They differ in scope, structure, and purpose, but both provide standardised terminology for describing mental and behavioural conditions.
| ICD | DSM | |
|---|---|---|
| Publisher | World Health Organisation (WHO) | American Psychiatric Association (APA) |
| Scope | Classification of diseases and health conditions worldwide | Mental disorders |
| Use | Diagnosis, health statistics, communication, and other health-system purposes | Clinical, research, and educational use, particularly in the United States |
| Approach | Descriptive and health-system oriented | Detailed diagnostic criteria and operationalised descriptions |
Both systems aim to support communication, research, statistics, and clinical work. Their categories are not explanations of everything that causes a person's difficulties. They are systems for organising and communicating about patterns.
ICD-10: The F-Category
In ICD-10, mental and behavioural disorders are coded under the F-category, with groups ranging from F0 to F9:
| Code | Group |
|---|---|
| F0 | Organic (including symptomatic) mental disorders |
| F1 | Mental and behavioural disorders due to psychoactive substances |
| F2 | Schizophrenia, schizotypal and delusional disorders |
| F3 | Affective (mood) disorders |
| F4 | Neurotic, stress-related and somatoform disorders |
| F5 | Behavioural syndromes associated with physiological disturbances |
| F6 | Personality and behaviour disorders |
| F7 | Intellectual disability (historically termed “mental retardation” in ICD-10) |
| F8 | Developmental disorders |
| F9 | Behavioural and emotional disorders with onset in childhood and adolescence |
Each code can be further specified by additional digits — for example, F10.0 for acute intoxication due to alcohol and F32.1 for a moderate depressive episode.
ICD-11: What Changed and Why
ICD-11, which came into effect in January 2022, introduced significant changes to the classification of mental and behavioural conditions. National implementation has taken place at different speeds.
| ICD-10 | ICD-11 | Why |
|---|---|---|
| Affective disorders | Mood disorders | More precise focus on the core clinical presentation. |
| Neurotic, stress-related, somatoform | Anxiety/obsessive-compulsive, stress-related and related disorders | Greater separation according to functional and clinical patterns. |
| Personality disorders (multiple types) | Personality disorder with severity and trait-based description | A more integrated model rather than multiple separate categories. |
| Mental retardation | Disorders of intellectual development | Updated terminology and a focus on developmental and support needs. |
| Mental and behavioural disorders due to psychoactive substances | Disorders due to substance use and related conditions | Clearer differentiation of substance-related conditions. |
The shift reflects several broader developments:
- Lifespan approach — disorders are considered across the lifespan rather than being rigidly separated by age.
- Functional criteria — severity and impairment receive greater attention alongside symptoms.
- Cultural sensitivity — cultural differences are given greater consideration.
- Reduced stigma — terminology is updated where older language may be devaluing or stigmatising.
The Limits of Classification
Classification systems are tools. They create order, enable communication, support research, and help structure clinical thinking. But they have limits.
Psychological difficulties do not always separate cleanly. Symptoms overlap. Individual life circumstances, biographical experiences, and personal coping strategies can be difficult to capture within standardised categories.
A diagnosis describes a pattern of symptoms — not a person's identity, history, or personality. It is a necessary approximation, not a definition.
There is a tension here: between the need for standardisation and the need to do justice to the individual. Classification offers orientation. For me, this is where classification reaches its limit: the category can describe a pattern, but it cannot describe the whole person.
ICF — Seeing What People Can Do
There is a system that complements classification: the ICF (International Classification of Functioning, Disability and Health). It approaches health from a different angle, looking at functioning, activities, participation, personal factors, and the environment in which a person lives.
This matters because a diagnosis can help describe a disorder, while the ICF shifts attention toward functioning — what a person can do, where they experience difficulty, what supports them, and what remains possible.
What I Take From This
One: A diagnosis is a framework — not the person.
Diagnostic categories are useful. They help organise patterns and communicate about them. But they are not the person. They describe a pattern; they do not describe a life.
Two: Every system reflects its time.
The triadic system, ICD-10, ICD-11, and DSM each reflect the assumptions and knowledge of their eras. None is final. None is neutral. If I forget that, I risk confusing the label with the person.
Three: What people can do matters too.
For me, the important lesson is not to look only at what is impaired. Functioning, resources, possibilities, and context matter too. What remains is part of the picture.
My takeaway: A classification can help me name a pattern, but it should never become a substitute for seeing the person behind the label.
MY REFLECTION:
I used to think a diagnosis was something you find — like a coin under a pillow. You look for it, you find it, you hold it up, and there it is: depression. Anxiety. PTSD. Found.
It is not quite like that. A diagnosis is an agreement — a framework developed to describe a particular pattern of symptoms. The pattern is real. The suffering is real. But the label is a tool, not the whole truth. And tools can be improved. They can be replaced. Sometimes, they can be wrong.
That does not shake me. It steadies me. Because if a diagnosis is not the whole truth, I am free to hold it lightly — to use it for orientation, not definition. To say, “This pattern fits what I see,” rather than, “This person is this pattern.”
The person is always more than the pattern.
That, for me, is where understanding begins.
References
- World Health Organisation (WHO) — International Classification of Diseases (ICD)
- World Health Organisation (WHO) — International Classification of Functioning, Disability and Health (ICF)
- American Psychiatric Association (APA) — Diagnostic and Statistical Manual of Mental Disorders (DSM)
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