Classification & Assessment in Psychiatry · Paper A
Depersonalisation and derealisation
DepersonalisationThe unsettling feeling of being detached from one's own body, thoughts, or sense of self.Read more → and derealisationThe unsettling feeling that the outside world feels unreal, distant, or dreamlike.Read more → are unsettling but usually benign experiences that are often mistaken for a more serious loss of touch with reality. Take someone who feels as though they are watching themselves from outside their own body, e.g. like an actor watching their own film, yet knows this feeling is not literally true. In practice, that retained awareness that the experience is 'just a feeling' is what keeps it well short of psychosis.
DepersonalisationThe unsettling feeling of being detached from one's own body, thoughts, or sense of self.Read more → is a sense of detachment from oneself, such as watching oneself as an observer or feeling unreal or robotic. DerealisationThe unsettling feeling that the outside world feels unreal, distant, or dreamlike.Read more → is the world itself feeling unreal, flat or dreamlike. Crucially, insightA person's awareness and understanding that they are unwell and need help.Read more → is retained: the person knows these are subjective experiences, not objective reality, which distinguishes them from psychosis, such as the nihilistic Cotard delusionA fixed false belief, held with total conviction, that is not shared by the person's culture and is not changed by evidence against it.Read more →, held with full conviction that one is dead. Depersonalisation and derealisation are common and often triggered by anxiety, fatigue or cannabis, and they only become a disorder when persistent and distressing. Take two patients who both say 'I feel unreal', e.g. one adds 'but I know it's just a feeling' while the other insists they are actually dead: asking directly whether the patient believes the experience or merely feels it is what separates depersonalisation from a delusion.
A patient telling you "I feel unreal" could be describing something benign and common, or something that signals a completely different, more serious diagnosis: and the way to tell the two apart is one of the highest-yield discriminators in the whole exam. and are common experiences that most people encounter briefly at some point, so knowing exactly when they cross into pathology, and what they are not, matters as much as knowing what they are.
is a subjective sense of detachment from oneself, described by patients as watching themselves from outside their own body, feeling unreal, robotic, or as though they are an actor playing themselves rather than genuinely living the moment. Derealisation is the closely related experience of the external world itself feeling unreal, flat, dreamlike or somehow artificial, as though seen through a pane of glass or a film screen. The two frequently occur together and are often described together as depersonalisation-derealisation syndrome (a recognised clinical presentation combining both experiences) when they become persistent and distressing enough to warrant a formal diagnosis in their own right.
The single most important feature of and , and the one most heavily tested in exams, is that (an accurate awareness that one's own experience is subjective, rather than an objectively true fact about the world) is retained throughout. The person knows, even while experiencing the sensation intensely, that these are subjective feelings rather than objective reality; they feel unreal, but they know, on reflection, that they are not. This retained insight is exactly what distinguishes depersonalisation from psychosis.
The clearest contrast is the Cotard delusion (a nihilistic delusion in which a person holds the fixed, false belief that they are dead, do not exist, or have lost their internal organs), which is held with full, unshakeable conviction rather than experienced as a passing subjective feeling. Take two patients who both say 'I feel unreal', e.g. during a routine mental state examination on the ward. The first adds, unprompted, 'but I know it's just a feeling, I'm not actually dead or gone'; the second insists, with complete conviction and no doubt whatsoever, that they genuinely are dead. Asking directly whether a patient believes the experience to be objectively true, or merely feels that way subjectively, is the single most useful clinical question for telling apart from a delusion.
and are common experiences in the general population and are frequently triggered by anxiety, panic attacks, severe fatigue, sleep deprivation, or cannabis and other recreational drug use. Brief episodes lasting seconds to minutes are widely reported by people with no psychiatric diagnosis at all, especially during or immediately after a panic attack. These experiences only become a formal disorder, depersonalisation-derealisation disorder, once they are persistent, recurrent and cause significant distress or genuine functional impairment, rather than being a one-off, transient sensation that resolves on its own. A patient develops a sudden sense of watching herself from a distance during a crowded train journey, shortly after a panic attack earlier that day; she is deeply frightened that she is 'going mad', but on direct questioning confirms she knows this is just a feeling and does not truly believe it is literally happening.
Dissociative amnesia (a gap in autobiographical memory, typically for stressful or traumatic material, without a clear organic cause) is a different phenomenon from : autobiographical memory itself stays fully intact in depersonalisation, and only the sense of self or reality is altered. Depression and anxiety disorders are common comorbidities and can themselves feature depersonalisation as a secondary symptom, so a broader mood and anxiety history should always be taken alongside the specific depersonalisation history. epilepsy and other organic causes should be considered and actively screened for if the presentation is atypical, for instance if episodes are very brief, stereotyped and associated with other seizure features, since these organic mimics need a different diagnostic pathway, including imaging or EEG investigation, rather than a purely psychological approach.
Assessment centres on a careful history establishing the phenomenology, triggers, duration and, crucially, the presence of retained , alongside screening for depression, anxiety and substance use, which are the commonest underlying drivers. Diagnostic criteria under ICD-11 and DSM-5 both require persistent or recurrent or experiences with intact reality testing, causing clinically significant distress or functional impairment before a formal diagnosis is made.
There is no single licensed first-line medication specific to - disorder; management instead focuses on treating an underlying anxiety or depressive disorder where present, using standard first-line pharmacological and psychological therapy for that underlying condition per NICE guidance, alongside structured psychoeducation. Simply explaining the retained- distinction to a frightened patient, and reassuring them that the experience is a recognised, benign anxiety-related phenomenon rather than a sign of impending psychosis, can itself be genuinely therapeutic, meaningfully reducing the secondary fear that often maintains and worsens the symptom.
The pearl is a single question, not a checklist: "do you believe this is really happening, or does it just feel that way?" A patient who answers "it just feels that way" has retained and is describing or ; a patient who answers with total conviction that it IS happening is describing a , and that one question does more diagnostic work than a page of description.
and are unreality experienced with retained : the moment insight is lost and the belief becomes fixed, you are no longer dealing with depersonalisation, you are dealing with psychosis.