dissociative identity disorder

**Definition (DSM-5-TR):** - Disruption of identity with two or more distinct personality states (may be described as possession in some cultures), involving marked discontinuity in sense of self and agency, with changes in affect, behavior, consciousness, memory, perception, cognition, and/or sensorimotor function. - Recurrent gaps in recall of everyday events, important personal information, and/or traumatic events, inconsistent with ordinary forgetting. - Causes clinically significant distress or impairment. - Not a normal part of a broad cultural or religious practice (e.g., in children, not better explained by imaginary playmates). - Not due to substances (e.g., blackouts, chaotic behavior in alcohol intoxication) or another medical condition (e.g., complex partial seizures).

**Pathophysiology/Etiology:** - Strongly linked to severe, chronic childhood trauma (sexual/physical abuse, neglect) before about age 6-9, when a cohesive sense of self is still developing. - Dissociation is thought to be a defense mechanism/coping strategy to compartmentalize overwhelming experiences. - Neurobiologic findings (e.g., altered hippocampal/amygdala volumes, frontolimbic dysregulation) are suggestive but not diagnostic.

**Epidemiology:** - Female predominance in clinical samples; prevalence about 1-1.5% in community samples. - Often diagnosed in young adulthood but with years of delay; patients commonly present with other complaints.

**Clinical features:** - Identity "alters" with different names, ages, genders, mannerisms, and memories. A host/primary identity is often unaware of the others. - Amnesia (dissociative amnesia is the core feature), fugue episodes, depersonalization/derealization. - Hearing voices (usually internal and experienced as from alters, not true psychosis). - Frequent comorbidities: PTSD, depression, anxiety, substance use, borderline personality disorder, somatic symptoms, self-harm, and high suicide risk (about 70% attempt).

**Differential diagnosis (high-yield):** - Dissociative amnesia: memory loss only, no identity fragmentation. Dissociative fugue is a specifier of it (purposeful travel with amnesia and possible new identity). - Depersonalization/derealization disorder: detachment from self or surroundings with intact reality testing and no identity alters. - Schizophrenia: hallucinations/delusions plus negative symptoms, and no alternating identities. Voices are external. - Borderline personality disorder: unstable identity and affect but no distinct states with amnesia. - Malingering/factitious disorder, seizure disorders (temporal lobe epilepsy), substance-induced states, and PTSD.

**Management:** - Long-term trauma-focused psychotherapy is first-line, using a phase-oriented approach: (1) safety and stabilization, (2) trauma processing, (3) integration/rehabilitation. - CBT, DBT, and EMDR are used as adjuncts. - No FDA-approved medication for DID; treat comorbid depression, anxiety, or PTSD (e.g., SSRIs; prazosin for nightmares). - Hypnosis may be used cautiously because of the risk of false memories.

**Board pearls:** - Classic vignette: a patient with a childhood abuse history who has unexplained missing time, finds unfamiliar items, is called by different names by others, and has multiple distinct personalities. - Do not confuse with schizophrenia ("split personality" is a misnomer for schizophrenia, which means a split from reality). - Dissociation is a mature versus immature defense question: it is classified as an immature defense mechanism. - Dissociative disorders as a group: DID, dissociative amnesia, depersonalization/derealization disorder.