6 General adult psychiatry6.1 Psychiatric disorders in adulthood
6.1.6 Dissociative disorders
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Written by Resident Doctor Committee · Published
Definition and classification
Dissociation is an involuntary disruption of the normal integration of identity, sensation, memory, movement or behaviour, usually acute in onset and typically fluctuating.
In the International Classification of Diseases, 11th revision (ICD-11), dissociative disorders form their own grouping, separate from bodily distress, anxiety and health anxiety conditions.
ICD-11 separates trance disorder from possession trance disorder.
Disorder | What fails to integrate | Distinguishing feature |
|---|---|---|
Dissociative neurological symptom disorder | Motor, sensory or cognitive function | Loss of function inconsistent with recognised disease |
Dissociative amnesia, with or without fugue | Autobiographical memory | Gaps beyond ordinary forgetting |
Trance disorder | Awareness, movement and speech | Narrowed awareness without identity replacement |
Possession trance disorder | Personal identity | Identity felt to be replaced by an external agent, outside accepted cultural practice |
Dissociative identity disorder | Identity and executive control | Distinct identity states with recurrent changes in control |
Partial dissociative identity disorder | Identity | Dominant state with intrusive other states, without recurrent full changes in control |
Depersonalisation-derealisation disorder | Felt reality of self or surroundings | Persistent detachment or unreality with intact reality testing |
Dissociative amnesia and fugue
Dissociative amnesia is loss of autobiographical memory, with distress expressed mentally rather than physically, and it is not produced on purpose.
Dissociative fugue is unexplained, purposeful travel away from home with amnesia for the journey, usually after a stressor.
In fugue, attention, cognition and new learning are intact on testing, which separates it from delirium and dementia.
Dissociative neurological symptom disorder
Dissociative neurological symptom disorder (formerly conversion disorder) is a discrete, abrupt loss of neurological function, such as weakness or loss of speech, inconsistent with recognised disease.
It arises after a psychological stressor, often with calm unconcern about the deficit.
Investigations are normal, benzodiazepines bring no response, and the symptom is not produced intentionally or for gain.
Positive bedside signs support the diagnosis, but they do not show deception.
Sign | How it is elicited | What it shows |
|---|---|---|
Hoover's sign | Test voluntary hip extension, then hip extension while the opposite hip flexes against resistance | Weak voluntary extension becomes strong, so the motor pathway is intact |
Tremor entrainment | Ask for rhythmic tapping with the other limb | Tremor changes frequency, entrains or stops |
Hoover's sign is the positive sign of functional leg weakness.
Dissociative seizures
Retained memory for the period of apparent unresponsiveness is the most useful history feature favouring a dissociative (non-epileptic) seizure.
Injury, incontinence, stereotypy and reported onset from sleep occur in both conditions, so they do not discriminate.
Epilepsy and dissociative seizures can coexist, and video electroencephalography (EEG) of a typical event is often central.
Observed feature | Favours epilepsy | Favours dissociative seizure |
|---|---|---|
Eyes | Often open | Sustained closure |
Duration | Brief, often under two minutes | Longer or fluctuating |
Onset | Abrupt, or from EEG-confirmed sleep | May build gradually |
Movements | Automatisms | Variable or asynchronous |
Afterwards | Stertorous breathing, confusion | Quicker reorientation |
Ganser syndrome
Ganser syndrome is a dissociative state, classically in prisoners awaiting trial.
Its features are approximate answers, clouding of consciousness, pseudohallucinations, somatic conversion symptoms and later amnesia for the episode.
A single identity is retained, unlike dissociative identity disorder.
Approximate answers (vorbeireden, vorbeigehen) are the hallmark: wrong answers that are near misses of the correct reply.
Factitious disorder and malingering
Both involve deliberate production of symptoms and differ by motive, whereas dissociative symptoms are involuntary.
Condition | Motive | Notes |
|---|---|---|
Factitious disorder | Internal: the wish to occupy the sick role | Most severe form, with repeated admissions to different hospitals, is Munchausen syndrome |
Malingering | A clear external incentive | A behaviour, not a mental disorder; ICD-11 codes it outside the mental disorders chapter |
Intentional production needs evidence; inconsistency alone does not prove it.
Management
Explain the diagnosis positively: symptoms are real, and preserved functions can be used in rehabilitation.
Specialist physiotherapy retrains movement, and adapted cognitive behavioural therapy for dissociative seizures improves functioning and distress more consistently than seizure frequency.
Identity presentations need phased, trauma-informed therapy starting with stabilisation, avoiding suggestive memory recovery methods.