Many people occasionally experience a failure in the normal automatic integration of memories, perceptions, identity, and consciousness. For example, people may drive somewhere and then realize that they do not remember many aspects of the drive because they were preoccupied with personal concerns, listening to music or a podcast, or conversation with a passenger. Typically, such a failure, referred to as nonpathologic dissociation, does not disrupt everyday activities.
In contrast, people with a dissociative disorder may completely forget a series of normal behaviors occupying minutes, hours, days, or weeks and may sense a missing period of time in their experience. In dissociative disorders, the normal integration of consciousness, memory, perceptions, identity, emotion, body representation, motor control, and behavior is disrupted, and continuity of self is lost.
People with a dissociative disorder may experience the following:
Intrusions into awareness by loss of continuity of experience, including feelings of detachment from self (depersonalization) and/or the surroundings (derealization) and fragmentation of identity.
Memory loss for important personal information (dissociative amnesia)
Brain research in animals and humans has begun to identify specific brain structures and functions underlying dissociation. In particular, during dissociation rhythmic activity occurs in a deep posteromedial region, including the posterior cingulate cortex, that is disconnected from higher cortical regions responsible for thought and planning (1). Similarly, during hypnosis there is a relative disconnection of those higher control regions from a portion of the back of the brain (the posterior cingulate cortex) that is involved in self-reflection (2). In addition, trauma-related dissociation appears to involve increased activation of the ventromedial prefrontal cortex and decreased connectivity with the cerebellum and orbitofrontal cortex (3).
Distinguishing Dissociative Disorders from Trauma and Stressor-related Disorders
Dissociative disorders frequently develop after overwhelming psychological stress or trauma (1), generated by traumatic events or by intolerable inner conflict. Dissociative disorders, therefore, are related to trauma and stressor-related disorders, including acute stress disorder and posttraumatic stress disorder (PTSD), both of which can include dissociative symptoms (eg, amnesia, flashbacks, numbing, depersonalization/derealization). Distinguishing dissociative disorders, including dissociative amnesia and dissociative identity disorder, from PTSD can be a clinical challenge. The diagnostic approach depends upon the predominant symptoms and the final diagnosis may be:
Post-traumatic stress disorder, with dissociative symptoms
Acute stress disorder, with dissociative symptoms
Dissociative amnesia
Dissociative identity disorder
Complex post-traumatic stress disorder
If the full array of PTSD symptoms (intrusion, avoidance, demoralization, and hyperarousal) are present, the appropriate diagnosis is typically PTSD. A dissociative subtype of PTSD exists to classify patients who meet all the diagnostic criteria for PTSD but also experience depersonalization, derealization, or both in response to the stressor (4). Similarly, dissociative symptoms are included in the diagnostic criteria for acute stress disorder. However, if the primary symptoms are dissociative, do not arise in the aftermath of a specific trauma or traumas, and the standard PTSD symptoms are not apparent, then a dissociative disorder diagnosis is more appropriate. Dissociative identity disorder typically arises in the wake of a series of abusive experiences in childhood.
Flashbacks often involve not only reliving of previous traumatic experiences with accompanying intense affect, but also may involve temporary amnesia for subsequent events. For example, during a traumatic combat-related flashback a soldier may experience doubt about surviving that is similar to the doubt experienced at the time of the original trauma, thus displaying dissociative amnesia for surviving the original event. Conversely, if the predominant symptomatology of a person with dissociative symptoms involves identity fragmentation and amnesia for elements of experience when one or another component of identity predominates, dissociative identity disorder (DID), rather than dissociative amnesia, is the appropriate diagnosis.
Another diagnostic possibility is complex PTSD, which is described in the ICD-11 but not included in the DSM-5-TR, is characterized not only by major PTSD symptoms, but by disturbances of self-organization, affective dysregulation (intense and unpredictable mood swings, difficulty controlling emotions), and negative self-concept (feeling worthless, hopeless, or guilty), in addition to disturbed relationships (difficulty maintaining healthy relationships, and feeling detached or alienated from others) (5–7).
References
1. Vesuna S, Kauvar IV, Richman E, et al. Deep posteromedial cortical rhythm in dissociation. Nature. 2020;586(7827):87-94. doi:10.1038/s41586-020-2731-9
2. Jiang H, White MP, Greicius MD, Waelde LC, Spiegel D. Brain Activity and Functional Connectivity Associated with Hypnosis. Cereb Cortex. 2017;27(8):4083-4093. doi:10.1093/cercor/bhw220
3. Lebois LAM, Harnett NG, van Rooij SJH, et al. Persistent Dissociation and Its Neural Correlates in Predicting Outcomes After Trauma Exposure [published correction appears in Am J Psychiatry. 2022 Aug;179(8):585. doi: 10.1176/appi.ajp.21090911correction.]. Am J Psychiatry. 2022;179(9):661-672. doi:10.1176/appi.ajp.21090911
4. Diagnostic and Statistical Manual of Mental Disorders, 5th edition, Text Revision (DSM-5-TR). American Psychiatric Association Publishing, Washington, DC, pp 329-348.
5. Rie S, Kruijt S, Stojimirović E, van der Aa N, Boelen PA. Posttraumatic Stress Disorder and Dissociation in a Clinical Sample of Refugees in the Netherlands: Evidence for a Dissociative Subtype. J Trauma Dissociation. 2025;26(2):261-279. doi:10.1080/15299732.2024.2448429
6. Hamer R, Bestel N, Mackelprang JL. Dissociative Symptoms in Complex Posttraumatic Stress Disorder: A Systematic Review. J Trauma Dissociation. 2024;25(2):232-247. doi:10.1080/15299732.2023.2293785
7. Hyland P, Hamer R, Fox R, et al. Is Dissociation a Fundamental Component of ICD-11 Complex Posttraumatic Stress Disorder?. J Trauma Dissociation. 2024;25(1):45-61. doi:10.1080/15299732.2023.2231928
