How our understanding of trauma and dissociation changed

The explanation kept changing

Dissociation has been around for a long time before psychiatry finally gave it a name. People had long described memory gaps, altered states, involuntary actions, bodily symptoms without an obvious injury, and sudden changes in behaviour.¹

One of the surprising things about trauma history is that knowledge did not simply accumulate. Physicians repeatedly connected overwhelming experiences with psychological symptoms, then later generations forgot, rejected, or reinterpreted those ideas. The history is full of rediscoveries!¹²

At different points, those experiences were blamed on the body, spirits, fragile nerves, heredity, weak character, fantasy, or overwhelming events. Those explanations reflected more than medicine. They also reflected who society trusted, what it believed about women and children, and whether suffering was seen as an injury or a personal failing.¹

Before psychiatry had a name for it

Ancient and medieval accounts include mutism, apparent paralysis, convulsions, amnesia, nightmares, altered behaviour, and periods of ordinary life interrupted by strikingly different states.¹ They show that people noticed experiences which modern clinicians might now sort across dissociative, neurological, trauma-related, sleep, and other conditions.

Across all of these periods, one question appears again and again: is the person reacting to an injurious world, or revealing a defect within themselves? Nijenhuis traces how explanations have moved back and forth between those poles.¹

Hysteria wasn't one illness

The meaning of hysteria kept changing. Hippocratic writers discussed illnesses associated with the womb; later writers built a much broader category and then projected it backward onto ancient texts.³

By the nineteenth century, hysteria could cover symptoms that would now be spread across dissociative disorders, functional neurological disorder, epilepsy, trauma-related conditions, and more. It was not diagnosed only in women, but it was strongly gendered.³ Women's pain, fear, anger, sexuality, and resistance were often interpreted through assumptions about sensitivity, reproduction, and dependence.

When possession explained a change in self

Some accounts of possession include changes in voice or behaviour, gaps in awareness, inner conflict, and the feeling that another force has taken control. Modern readers may recognise parts of those descriptions.¹

This doesn't necessarily mean those experiences lined up perfectly with what we know now as DID. Possession can be part of accepted religious practice, a way of expressing distress, a neurological or psychiatric condition, deliberate performance, or several of those things at once.³

Janet asked a different question

Pierre Janet worked with patients whose memories, emotions, and actions seemed to run along different tracks. Rather than treating them as weak or deceptive, he asked what might happen when an overwhelming experience never became fully integrated into ordinary consciousness and memory.⁴

In Janet's account, the experience did not simply disappear. Sensations, actions, emotions, and memories could remain separated from ordinary awareness and return through intrusions, bodily symptoms, re-enactments, or altered states.⁴

His work helped establish a way of thinking about dissociation as organised around memory, emotion, and integration rather than as a simple act of avoidance.⁴

A railway accident and an argument

Nineteenth-century doctors were increasingly confronted with people who had pain, fear, memory problems, paralysis, or disturbed sleep after accidents and violence, sometimes without an obvious physical lesion. Railway accidents became one public argument over whether fright itself could injure a person.¹

Money and legal responsibility were at stake. If psychological injury counted as a real injury, railway companies could be held responsible. If symptoms were dismissed as weakness or fraud, responsibility largely disappeared.¹

The same gap appeared in accounts of child abuse. In nineteenth-century France, forensic physician Auguste Ambroise Tardieu painstakingly documented abuse of children. The evidence existed. What often failed was connecting those experiences to later psychological suffering.¹ Knowing that harm happened and recognising what it did to a person have not always arrived together.

War changed the argument

The First World War made psychological injury difficult to ignore. Soldiers experienced tremors, paralysis, mutism, nightmares, memory loss, altered states, and emotional collapse. Terms such as shell shock and war neurosis reflected competing theories about whether the injury belonged to the brain, nerves, mind, or character.⁵

Ask someone to picture shell shock and they will probably picture a man returning from the trenches. Women were there too, including nurses, but they are easy to lose from that familiar image.⁵ Even among soldiers, the response depended on class, rank, and whether the military still considered a man useful. One man might be treated as injured. Another could be called a coward or accused of faking.

Men are still expected to absorb danger, stay useful, and keep quiet about what it costs them. “Male disposability” is one political name for that bargain. In 2021, the global male suicide rate was more than twice the female rate.⁶ Research also links traditional masculine norms with self-stigma and negative attitudes toward seeking psychological help.⁷ PTSD and dissociation are both associated with suicidal behaviour, though neither explains every death.⁸⁹

A diagnosis built around the event

Post-traumatic stress disorder entered DSM-III in 1980. The change grew out of research and advocacy involving Vietnam veterans, Holocaust survivors, survivors of sexual trauma, and others.¹⁰

The introduction of PTSD marked a turning point. Rather than asking what kind of person develops these symptoms, psychiatry was now explicitly asking what kind of event had happened to them.¹⁰ It also marked a shift in responsibility. Trauma could reflect what had happened to an otherwise ordinary person, not only a sign of individual weakness.¹⁰

When “multiple personality” became DID

Ideas about divided consciousness, amnesia, automatisms, hypnosis, and alternating states had circulated for decades before a modern diagnostic category was created.⁴ Multiple personality disorder entered DSM-III in 1980. It was renamed dissociative identity disorder in DSM-IV in 1994.¹¹

"Multiple Personality" suggests that several people or personalities inhabit the same body. “Dissociative identity” instead points to discontinuity within one person's identity, memory, agency, and consciousness.¹¹

Researchers still disagree about how DID develops, the role of memory and culture, and whether treatment shapes the way it appears. Current reviews describe a growing empirical literature alongside real limits in study quality, retrospective reporting, and diagnostic disagreement.¹²

Modern theories of DID grew out of this broader history. They inherited questions clinicians had been wrestling with for more than a century: what happens when overwhelming experiences cannot be integrated into a coherent sense of self?⁴

Nijenhuis, E. R. S. (2015). The trinity of trauma: Ignorance, fragility, and control, Volumes I and II. Vandenhoeck & Ruprecht. Volume I, historical accounts of trauma, hysteria, war neurosis, and dissociation. Historical and theoretical account. The author advances a particular trauma and structural-dissociation framework, so interpretive claims are identified as his perspective. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹
Herman, J. L. (1992). Trauma and recovery: The aftermath of violence, from domestic abuse to political terror. Basic Books. Historical account of trauma recognition and its social context. Influential historical and clinical synthesis of trauma, including the recurring recognition and neglect of trauma-related suffering. ↩
King, H. (1993). Once upon a text: Hysteria from Hippocrates. In Hysteria beyond Freud (pp. 3-90). University of California Press. Historical interpretation of Hippocratic texts and later constructions of hysteria. Historical scholarship cautioning against treating ancient writings as a single continuous psychiatric diagnosis. ↩ ↩² ↩³
van der Hart, O., & Horst, R. (1989). The dissociation theory of Pierre Janet. Journal of Traumatic Stress, 2(4), 397-412. Abstract. Historical account of Janet's theory of dissociation as a response to overwhelming experience and of his concepts of memory, emotion, and psychological integration. ↩ ↩² ↩³ ↩⁴ ↩⁵
Loughran, T. (2013). A crisis of masculinity? Re-writing the history of shell-shock and gender in First World War Britain. History Compass, 11(9), 727-738. Abstract. Historical review of how war trauma was interpreted through gender and social context, cautioning against a single account of shell shock. ↩ ↩²
World Health Organization. (2025). Suicide worldwide in 2021: Global health estimates. p. 4, Global epidemiology of suicide. WHO estimates showing a global age-standardized suicide rate of 12.3 per 100,000 for males and 5.6 for females in 2021. ↩
Üzümçeker, E. (2025). Traditional masculinity and men's psychological help-seeking: A meta-analysis. International Journal of Psychology, 60(2), e70031. Abstract; meta-analysis of 35 samples. Meta-analysis associating stronger endorsement of traditional masculinity with more negative help-seeking attitudes and greater self-stigma. ↩
Akbar, R., Arya, V., Conroy, E., Wilcox, H. C., & Page, A. (2023). Posttraumatic stress disorder and risk of suicidal behavior: A systematic review and meta-analysis. Suicide and Life-Threatening Behavior, 53(1), 163-184. Abstract; systematic review and meta-analysis. Meta-analysis finding associations between PTSD and death by suicide, attempted suicide, and suicidal ideation. ↩
Calati, R., Bensassi, I., & Courtet, P. (2017). The link between dissociation and both suicide attempts and non-suicidal self-injury: Meta-analyses. Psychiatry Research, 251, 103-114. Abstract. Meta-analysis of 19 studies comparing suicide attempts and non-suicidal self-injury in psychiatric patients with and without dissociative disorders. ↩
National Center for PTSD. (n.d.). History of PTSD in veterans: Civil War to DSM-5. PTSD added to DSM-III in 1980; veteran, feminist, and Holocaust-survivor advocacy. VA overview of the historical development of PTSD and the research and advocacy contributing to its inclusion in DSM-III. ↩ ↩² ↩³
Young, M., Almaskati, M., Vrabtchev, S., & Kuruvilla, T. (2024). Dissociative identity disorder: A review of the diagnosis that divides. Progress in Neurology and Psychiatry, 28(2), 23-27. Diagnostic history and current DSM/ICD descriptions. Clinical review of DID's diagnostic history, classifications, controversies, and current clinical implications. ↩ ↩²
Dorahy, M. J., Brand, B. L., Sar, V., Kruger, C., Stavropoulos, P., Martinez-Taboas, A., Lewis-Fernandez, R., & Middleton, W. (2014). Dissociative identity disorder: An empirical overview. Australian and New Zealand Journal of Psychiatry, 48(5), 402-417. Abstract and review scope. DID-specific empirical overview that discusses accumulating evidence, ongoing controversy, and research limitations. ↩

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