Classification in psychiatry accounts for approximately 17% of Paper A marks and underpins diagnostic questions in Paper B. The transition from ICD-10 to ICD-11 (adopted by WHO member states in 2022) is the most significant change to psychiatric classification in a generation and is a high-yield topic for the current exam sitting. The exam tests both knowledge of diagnostic criteria AND awareness of the structural changes between editions.
What Changed in ICD-11: A Summary
The ICD-11 classification of mental, behavioural, or neurodevelopmental disorders represents the first major revision since ICD-10 (1992). ICD-11 was adopted at the World Health Assembly in May 2019 and came into effect for WHO member states on 1 January 2022. The UK has transitioned to ICD-11 coding, and the MRCPsych now expects candidates to be familiar with ICD-11 criteria.
Key structural changes:
- Reorganisation of diagnostic groupings (e.g., OCD and related disorders separated from anxiety disorders; gender identity disorders moved to a new chapter on conditions related to sexual health)
- Dimensional model for personality disorders (replacing categorical ICD-10 types)
- Simplification of criteria for several disorders (schizophrenia, depressive episode, PTSD)
- New diagnoses: complex PTSD, prolonged grief disorder, gaming disorder, body integrity dysphoria, olfactory reference disorder
- Removal of some ICD-10 diagnoses: schizophrenia subtypes, dysthymia (replaced by persistent mood disorders), hypochondriasis (replaced by health anxiety / illness anxiety disorder)
- Lifespan approach: childhood and adult diagnoses integrated in the same chapter structure
- Eliminated the ICD-10 requirement for social and occupational impairment in some diagnoses
Personality Disorders: The Biggest Change
The ICD-11 replaced the 10 categorical personality disorder types from ICD-10 with a single dimensional diagnosis of personality disorder, graded by severity (mild, moderate, or severe) based on the degree of impairment in self-functioning (identity, self-direction) and interpersonal functioning (empathy, intimacy). The candidate assigns one or more of five trait domain qualifiers: negative affectivity, detachment, dissociality, disinhibition, and anankastia. The borderline pattern specifier was retained because of its specific treatment implications (DBT, MBT). The exam tests this change directly: “Which ICD-10 personality disorder categories are no longer recognised in ICD-11?” — all of them, replaced by the dimensional model with the borderline pattern specifier. Schizotypal disorder was moved out of the PD chapter and into the schizophrenia spectrum chapter (as schizotypal disorder, not schizotypal PD).
Schizophrenia and Psychotic Disorders
ICD-11 removed all schizophrenia subtypes (paranoid, hebephrenic, catatonic, undifferentiated, residual) that existed in ICD-10. The diagnosis of schizophrenia now requires at least 1 of the following symptoms present for most of the time over at least 1 month: persistent delusions, persistent hallucinations, disorganised thinking, experiences of influence/passivity/control, or negative symptoms. The catatonic presentation is now specified as a separate entity (catatonia associated with another mental disorder) rather than a subtype of schizophrenia. Schizoaffective disorder remains but with stricter criteria requiring that mood and psychotic symptoms occur together for most of the illness duration. This is a change from ICD-10 where the mood symptoms needed to meet criteria for a mood episode for a “substantial part” of the total illness duration.
Depressive Disorders
ICD-11 simplified the criteria for depressive episode. The ICD-10 requirement of at least 2 of 3 typical symptoms (depressed mood, loss of interest, reduced energy) was retained. However, the number of additional symptoms was simplified: mild requires 2 core + 2-3 additional, moderate requires 2 core + 4-5 additional, severe requires all 3 core + 5+ additional. The symptom list was streamlined. Dysthymia (chronic low-grade depression in ICD-10) was replaced by persistent depressive disorders (chronic depression lasting at least 2 years, which may include dysthymic presentations). The ICD-10 concept of recurrent brief depressive disorder was retained. Mixed anxiety and depressive disorder (ICD-10 F41.2) was retained but reconceptualised.
Trauma and Stress-Related Disorders
PTSD was simplified to 3 core clusters (re-experiencing, avoidance, hypervigilance) from ICD-10’s 6 clusters. This makes the diagnosis more specific and reduces overlap with other conditions. Complex PTSD was added (see the anxiety disorders article). Prolonged grief disorder was added (persistent grief lasting >6 months). Adjustment disorder criteria were tightened with a 1-month onset requirement and a 6-month maximum duration. Reactive attachment disorder and disinhibited social engagement disorder were retained for children.
Obsessive-Compulsive and Related Disorders
This new chapter separates OCD from anxiety disorders (ICD-10’s grouping). The chapter includes: OCD, body dysmorphic disorder, olfactory reference disorder (preoccupation with perceived body odour, new to ICD-11), hypochondriasis (illness anxiety disorder), hoarding disorder, trichotillomania, and excoriation disorder. The insight specifier (good/fair, poor, absent/delusional) is used across all these conditions.
Feeding and Eating Disorders
ICD-11 retained anorexia, bulimia, and binge-eating disorder (which was not in ICD-10 but is now included). The amenorrhea requirement for anorexia was removed. ARFID (avoidant/restrictive food intake disorder) was added, capturing conditions like picky eating that result in nutritional deficiency without body image disturbance. Pica and rumination disorder were retained.
Neurodevelopmental Disorders
Autism spectrum disorder replaced the ICD-10 subtypes (childhood autism, Asperger syndrome, atypical autism, Rett syndrome, other childhood disintegrative disorder). Rett syndrome was moved to the developmental anomalies chapter. ADHD criteria were tightened: onset required before age 12 (ICD-10 required before age 7). Intellectual disability (the ICD-11 diagnostic term) replaced mental retardation. The severity is now graded primarily by adaptive functioning.
Other Notable Changes
- Gaming disorder: Added as a new diagnosis (pattern of gaming behaviour with impaired control, increasing priority, and continuation despite negative consequences for at least 12 months)
- Body integrity dysphoria: The desire to have a specific physical disability (wanting amputation of a healthy limb, wanting to be blind or paralysed). Distinguished from Munchausen syndrome by the absence of secondary gain and the specific focus on body integrity.
- Catatonia: Now classified as a separate diagnostic entity (catatonia associated with another mental disorder and catatonia induced by substances/medications), not as a subtype of schizophrenia. This reflects the fact that catatonia occurs across a wider range of conditions.
- Gender incongruence: Removed from the mental disorders chapter and placed in a new chapter on conditions related to sexual health. This was a significant destigmatising change.
- Bipolar type II and cyclothymia were retained. The criteria for the manic/hypomanic episode were standardised (mania = 1 week, hypomania = 4 days, with requirement for increased activity/energy in addition to mood change).
High-Yield Exam Patterns for ICD-11 Changes
- Schizophrenia subtypes removed: Paranoid, hebephrenic, catatonic, undifferentiated, residual all out of ICD-11
- Personality disorders now dimensional: Severity (mild/moderate/severe) + trait specifiers. Borderline pattern specifier retained for treatment implications.
- Catatonia now a separate entity: Not a subtype of schizophrenia. Can be associated with any mental disorder.
- PTSD simplified to 3 clusters: Re-experiencing, avoidance, hypervigilance. Complex PTSD added.
- OCD separated from anxiety disorders: Now its own chapter (OCRDs) including BDD, hoarding, trichotillomania.
- ASD unified: Asperger, childhood autism, atypical autism all replaced by autism spectrum disorder.
- ADHD onset age changed: From <7 (ICD-10) to <12 (ICD-11). Three presentations: inattentive, hyperactive-impulsive, combined.
- Anorexia amenorrhea requirement: Removed in ICD-11
- Binge-eating disorder: New to ICD-11
- Gaming disorder: New diagnosis
- Gender incongruence: Moved out of mental disorders chapter
PsychStar’s question banks for both Paper A and Paper B reflect ICD-11 diagnostic criteria and test knowledge of the changes from ICD-10. Start with 5 free questions at psychstar.io/try.