Class presentation 1: how psychiatry organises disorders. Ten questions plus the take-home question. Based on DSM-5-TR (APA, 2022) and ICD-11 (WHO). Plan 15–20 minutes: about 8 slides.
Purpose: understand why psychiatric disorders are classified and how the major diagnostic systems organise them.
1. What does classification of mental disorders mean?
- Classification is the systematic grouping of mental disorders into named categories according to shared features (symptoms, course, duration, sometimes cause), with agreed definitions or criteria.
- It gives every disorder a name, a code and a set of rules for when the name may be used.
- Modern systems are descriptive (syndromal): they classify by what is observed and reported, because for most disorders the causes are not yet known.
- Two parts: nomenclature (the names) and diagnostic criteria (the rules for applying them).
2. Why do we classify mental disorders?
- A common language so clinicians, patients, families and services mean the same thing by "schizophrenia" or "depression".
- To guide treatment: the diagnosis points to evidence-based options (for example lithium for bipolar disorder, SSRIs plus CBT for depression).
- To give a prognosis and expected course.
- To communicate in referrals, records, courts and certificates.
- Research: groups of similar patients can be studied and compared.
- Public health: counting cases, planning services, budgets and drug supply, monitoring trends.
- Teaching and training.
3. The two major classification systems
| ICD-11 | DSM-5-TR | |
|---|---|---|
| Full name | International Classification of Diseases, 11th revision (Chapter 06: mental, behavioural or neurodevelopmental disorders) | Diagnostic and Statistical Manual of Mental Disorders, 5th edition, text revision |
| Published by | World Health Organization (WHO) | American Psychiatric Association (APA) |
4. What is the difference between DSM-5-TR and ICD-11?
| Feature | ICD-11 | DSM-5-TR |
|---|---|---|
| Scope | All diseases; mental disorders are one chapter | Mental disorders only |
| Official use | The international standard for health statistics, used by ministries of health (including Kenya's reporting system), insurers and WHO members | Mostly used in the USA and widely in research and teaching |
| Style | Clinical descriptions and diagnostic requirements, written for use in many settings and cultures, including low-resource ones | Detailed operational criteria (symptom counts, durations) |
| Cost | Free online | Paid publication |
| Personality disorder | Dimensional: one diagnosis graded by severity (mild, moderate, severe) with trait domains | Categorical (10 types) in the main text, with an alternative dimensional model |
| Examples of differences | Includes complex PTSD and gaming disorder; gender incongruence is moved out of the mental disorders chapter | PTSD without a separate complex form; prolonged grief disorder was added in the text revision |
What they share: the two have been harmonised so that the broad categories and many diagnoses line up, which makes research and records comparable.
5. Major categories of mental disorders, with examples
Roughly the same families appear in both systems:
- Neurodevelopmental: intellectual disability, autism spectrum disorder, ADHD.
- Schizophrenia spectrum and other psychotic disorders: schizophrenia, schizoaffective, brief psychotic disorder, delusional disorder.
- Mood disorders: bipolar and related (bipolar I and II, cyclothymia) and depressive (major depressive disorder, persistent depressive disorder).
- Anxiety disorders: generalised anxiety, panic disorder, phobias, social anxiety.
- Obsessive–compulsive and related: OCD, body dysmorphic disorder, hoarding.
- Trauma- and stressor-related: PTSD, acute stress reaction, adjustment disorder.
- Dissociative: dissociative amnesia, depersonalisation–derealisation.
- Somatic symptom and related: somatic symptom disorder, illness anxiety.
- Feeding and eating: anorexia nervosa, bulimia nervosa, binge eating.
- Sleep–wake: insomnia disorder, narcolepsy.
- Disruptive, impulse-control and conduct: oppositional defiant, conduct disorder.
- Substance-related and addictive: alcohol, opioid, cannabis, khat, gambling.
- Neurocognitive: delirium, major neurocognitive disorder (dementia).
- Personality disorders: borderline, antisocial, and others.
- Sexual dysfunctions, elimination disorders, paraphilic disorders and others.
6. Symptom, syndrome and disorder
| Term | Meaning | Example |
|---|---|---|
| Symptom | What the patient experiences and reports (subjective). A sign is what the examiner observes | Low mood, hearing voices; psychomotor slowing (sign) |
| Syndrome | A cluster of symptoms and signs that occur together and form a recognisable pattern | Depressive syndrome: low mood, anhedonia, poor sleep, guilt |
| Disorder | A syndrome that meets defined criteria (number of symptoms, duration, course), causes distress or impairment, and is not better explained by another condition, a substance or a normal reaction | Major depressive disorder: 5 of 9 symptoms for 2 weeks with impairment |
A symptom alone is not a diagnosis. Sadness is a symptom of many conditions and also part of normal life.
7. How does classification help in clinical practice?
- Structures history and examination (you know which symptoms to look for).
- Narrows the differential diagnosis and prompts investigations.
- Chooses treatment (medication, psychotherapy, psychosocial support) and the setting (outpatient or admission).
- Gives prognosis and helps counsel the patient and family.
- Supports legal and administrative steps: Mental Health Act admission, disability and sick leave, court reports.
- Allows audit and research on outcomes.
8. Limitations of psychiatric classification
- Categories versus dimensions: many conditions lie on a continuum with normal experience; cut-offs are partly arbitrary.
- Comorbidity is very common, which suggests the boundaries are blurred.
- Heterogeneity: one label covers many different presentations and causes.
- Reliability does not guarantee validity: clinicians can agree on a label without the label reflecting a real underlying disease.
- No biological markers yet confirm most diagnoses.
- Culture: criteria were developed mainly in high-income countries; symptoms are expressed and interpreted differently across cultures (for example somatic presentations of distress).
- Medicalising normal distress (grief, shyness, ordinary sadness).
- Stigma and labelling: a diagnosis can shape how a patient is treated and sees themselves.
- Based on symptoms, not causes, so it says little about why the person is ill.
- Revisions change boundaries over time.
9. Can two patients with the same diagnosis present differently?
Yes, very commonly. Criteria are usually polythetic: the patient needs some of a list, not all of it.
Simple example, major depressive disorder (5 of 9 symptoms needed):
- Patient A: low mood, insomnia, weight loss, agitation, guilt (melancholic).
- Patient B: low mood, oversleeping, weight gain, leaden fatigue, sensitivity to rejection (atypical).
- They share only low mood, yet both have the same diagnosis. Research suggests over 200 different symptom combinations satisfy the criteria for major depression.
- The same applies to schizophrenia (one patient mainly hallucinated, another mainly withdrawn and flat).
10. Clinical application
A 22-year-old university student for 3 weeks has been hearing voices that comment on what he does, believes the neighbours are spying on him, has barely slept and has stopped attending lectures.
- Broad category first considered: psychotic disorder (schizophrenia spectrum).
- Keep the alternatives open: a mood disorder with psychotic features (mania or depression), substance-induced psychosis (cannabis, khat, alcohol), and a medical or neurological cause (HIV, epilepsy, head injury, thyroid, delirium).
- Additional information needed before diagnosing:
- Duration and onset, and any previous episodes (3 weeks points away from schizophrenia, which needs 6 months in DSM-5-TR, and toward brief psychotic disorder or a substance or mood cause).
- Mood symptoms: elevated or depressed mood before or during the psychosis.
- Substance and medication history, urine drug screen.
- Medical and neurological history and examination; HIV status, thyroid, calcium, head imaging if indicated.
- Family history of psychosis or mood disorder.
- Collateral history from family or friends; premorbid functioning.
- Risk assessment: suicide, harm to others, vulnerability.
- Mental state examination and cognitive state (exclude delirium).
Take-home question: what can a diagnosis tell us, and what can't it?
It can tell us:
- The pattern of illness and what to look for, and a shared name for it.
- The likely course and prognosis, and the risks to watch for.
- Which treatments have evidence and what response to expect.
- What services and legal provisions may apply.
It cannot tell us:
- Why this person became ill, and why now (that is formulation: see the biopsychosocial formulation note).
- The person's life story, beliefs, culture and values, or what the symptoms mean to them.
- The severity and daily impact on function, or the person's strengths and supports.
- How they will personally respond to treatment, or what they want.
- Two people with the same diagnosis need different plans.
Closing line for the presentation: a diagnosis is a starting point for understanding a patient, never the end of it.
Presentation checklist
- Define classification and why we do it (2 slides)
- ICD-11 versus DSM-5-TR table (1 slide)
- Major categories with examples (1 slide)
- Symptom, syndrome, disorder (1 slide)
- Uses and limitations (1 slide)
- Same diagnosis, different patients, and the case example (1 slide)
- Take-home message (1 slide)