The History of Understanding Dissociation in Psychology

The Pioneers: 19th-Century Discoveries

In the mid-to-late 19th century, a handful of physicians working with patients in profound distress began to notice something remarkable: the mind seemed capable of dividing against itself. Memories, feelings, and even aspects of identity appeared to operate outside of a person’s ordinary awareness, shaping their behaviour without their knowledge or consent.

French neurologist Jean-Martin Charcot (1825–1893) was among the first to study these presentations systematically, working at the Salpêtrière hospital in Paris with patients whose symptoms defied straightforward neurological explanation.¹ Though his methods and terminology would not survive modern scrutiny, his careful clinical observations created the conditions for a new understanding of trauma, memory, and the mind. Several of the young doctors who trained under him would go on to reshape psychiatry entirely.

It was Charcot’s student Pierre Janet (1859–1947) who made the single most important contribution to our understanding of dissociation. In his foundational work L’automatisme psychologique (1889), Janet described how traumatic memories could become split off from ordinary consciousness, continuing to influence thought, feeling, and behaviour outside of a person’s awareness.² He coined the term dissociation (or in French, désagrégation) to describe this splitting process, and his ideas about “idées fixes” (fixed ideas) and the narrowing of consciousness under extreme stress form the basis of much modern trauma theory. Janet understood, over a century before the language existed, that trauma does not stay in the past.

At around the same time in Vienna, Josef Breuer and Sigmund Freud were working with patients whose experiences bore remarkable similarities to those Janet described. Their publication Studies on Hysteria (1895) included the famous case of “Anna O.”, a young woman whose dramatic and varied symptoms appeared linked to traumatic experiences and unprocessed grief.³ Breuer and the early Freud used hypnosis to access what seemed like split-off states of consciousness, language that closely parallels Janet’s framework. For a brief moment, the two strands of European psychiatry were pointing in the same direction.

Yet the paths of Janet and Freud would soon diverge in ways that would shape the next century of psychiatry, and not always for the better.

A Century of Neglect: How Dissociation Was Sidelined

As Freud’s influence grew, his model of repression came to dominate Western psychiatry. Rather than understanding symptoms as the result of trauma-induced dissociation, the psychoanalytic tradition shifted focus to unconscious drives, developmental conflicts, and internal defences.⁴ Trauma, particularly sexual trauma, was increasingly questioned or reframed. Freud’s abandonment of his seduction theory in the late 1890s had profound consequences: for decades, psychiatry would struggle to acknowledge the scale of harm that people, especially women and children, experienced at the hands of those close to them.

Janet’s work, written in French and less widely translated, reached far fewer readers than Freud’s. His concept of dissociation gradually slipped from mainstream discourse. By the mid-20th century, it had all but disappeared from psychiatric textbooks. Historian Henri Ellenberger, writing in 1970, described Janet as one of the great overlooked figures in the history of psychiatry: a man who had contributed foundational ideas about trauma, memory, and the unconscious, yet whose name was largely unknown outside specialist circles.⁵

This period of neglect had real consequences for people experiencing dissociation. Without a recognised framework, their experiences were often attributed to weakness, attention-seeking, or deliberate deception. The kind of compassionate, trauma-informed care that should have been standard was simply not available. Many of the misconceptions about dissociation that persist today have their roots in this era.

The Trauma Movement: Rediscovery in the Late 20th Century

The turning point came from an unexpected direction: the returning soldiers of the Vietnam War.

By the late 1970s, psychiatrists and psychologists working with veterans were documenting patterns of distress that existing frameworks could not adequately describe. Flashbacks, hypervigilance, emotional numbing, and fragmented memory were common. The existing diagnoses did not fit. Something had been systematically missed.

In 1980, the American Psychiatric Association published the third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III), which for the first time included Post-Traumatic Stress Disorder (PTSD) as a formal diagnosis.⁶ This was a watershed moment. It validated the experiences of trauma survivors and opened the door to recognising trauma as a major cause of psychological distress, not a minor or incidental factor.

Alongside the veterans’ movement, the women’s movement was drawing urgent attention to the scale of sexual violence and domestic abuse. Clinicians began to recognise that what had been diagnosed in women as “hysteria” or “borderline personality disorder” was often, in fact, the aftermath of repeated relational trauma. The understanding of the link between trauma and dissociation was slowly, painstakingly, being rebuilt.

Judith Herman’s book Trauma and Recovery, published in 1992, was transformative for the field.⁷ Herman drew explicit parallels between combat trauma and the experiences of women who had survived sexual and domestic violence. She described what she called “complex post-traumatic stress disorder” (Complex PTSD, or CPTSD) to capture the profound effects of prolonged, repeated traumatisation, including disruptions to identity, emotional regulation, consciousness, and relationships. The diagnostic categories within the DSM-III-R and DSM-IV formalised the dissociative disorders as a distinct clinical group, including what had previously been called multiple personality disorder, now renamed Dissociative Identity Disorder (DID).⁸

The Memory Wars: Controversy and Crisis in the 1990s

Progress was not without conflict. The 1990s saw a bitter and damaging debate about the validity of traumatic memories, particularly those recovered during therapy.

On one side were clinicians and survivors who had witnessed what appeared to be genuine traumatic memories emerging through therapeutic work. On the other, psychologists such as Elizabeth Loftus published extensive research demonstrating that memory is reconstructible, malleable, and vulnerable to suggestion.⁹ The concept of “false memory syndrome” entered public discourse, and accusations of therapist-implanted memories made headlines worldwide.

The fallout caused enormous harm. Survivors were disbelieved and publicly shamed. Clinicians became afraid to explore clients’ traumatic histories. Families accused of abuse organised politically to challenge their adult children’s experiences. The chilling effect on trauma treatment lasted for years.

What is now understood is that both truths can coexist. Memory is genuinely malleable and can, in some circumstances, be influenced by suggestion. Genuine traumatic memories of abuse are also real, valid, and well-documented. The debate was frequently weaponised to protect perpetrators and discredit survivors, and that weaponisation is one of the most troubling chapters in the history of dissociation research. Many of the common misconceptions about dissociation that circulate today trace back to this period of controversy.

Structural Dissociation Theory: A Modern Framework

The early 2000s brought a significant theoretical advance. Dutch clinicians and researchers Onno van der Hart and Ellert Nijenhuis, working alongside American therapist Kathy Steele, developed the Theory of Structural Dissociation of the Personality. Their 2006 book The Haunted Self synthesised decades of clinical research with Janet’s original 19th-century insights.¹⁰

Structural dissociation theory proposes that trauma fragments the personality into distinct “parts”: an Apparently Normal Part (ANP) that manages daily functioning, and one or more Emotional Parts (EPs) that remain fixed in traumatic experience, continuing to respond as if the danger is still present. This model applies across the full dissociation spectrum, from PTSD (one ANP and one EP) to Complex PTSD and DID (multiple ANPs and EPs), offering a coherent map of presentations that had previously seemed bewilderingly varied.¹¹

The theory has been influential because it provides clinicians and survivors alike with a workable framework: one that honours the protective intelligence behind dissociative responses, while also opening a path towards integration and healing. It reconnected modern trauma science with Janet’s original observation that traumatic memories do not simply fade, but continue to act on the person until they can be fully processed.

Bessel van der Kolk’s research and his widely read 2014 book The Body Keeps the Score brought many of these ideas to a general audience.¹² Van der Kolk argued powerfully that trauma is held in the body and nervous system, not simply in cognition or narrative memory, adding neuroscientific weight to what survivors have long described.

Dissociation in the DSM-5 and ICD-11

The most recent diagnostic revisions reflect a meaningfully more nuanced understanding of dissociation and its relationship to trauma.

The DSM-5 (2013) includes a dedicated chapter on dissociative disorders, covering DID, dissociative amnesia, and depersonalisation/derealisation disorder, as well as other specified and unspecified presentations.¹³ For the first time, the DSM-5 also introduced a dissociative subtype of PTSD, recognising that some people respond to trauma primarily through emotional detachment, derealisation, and depersonalisation rather than the classic hyperarousal pattern. This was a clinically significant step: it acknowledged that trauma can produce responses that look, on the surface, quite different from the most recognisable PTSD presentations.

The ICD-11 (World Health Organization, 2019) took an additional step by formally including Complex PTSD as a diagnosis, a development long advocated by clinicians working with survivors of prolonged traumatisation.¹⁴ This recognition matters enormously for people who have experienced repeated, relational trauma, particularly in childhood: it acknowledges that their difficulties are not a reflection of personal weakness or character, but of the documented psychological impact of sustained harm.

Together, these revisions represent the most comprehensive diagnostic recognition of dissociation and trauma-related experience in the history of psychiatry. There is still significant work to do, but the direction of travel is clear.

What This History Means for You

If you are living with dissociation today, this history matters in ways that go beyond academic interest.

It helps to explain why diagnosis can still be slow, why some clinicians remain uncertain or undertrained in dissociative conditions, and why the mental health system has not always responded with the understanding you deserve. The gaps in care you may have experienced are not random: they are the legacy of a century in which the field deliberately turned away from the reality of trauma.

Dissociation was not taken seriously for much of the 20th century because it was inconvenient. Acknowledging it fully required acknowledging the scale of harm that people, particularly women and children, experience within families and communities. That was, and remains, a difficult truth for many institutions to hold.

You are not imagining your experience. The symptoms you carry, including dissociative episodes, gaps in memory, fragmented sense of self, and the feeling of being disconnected from your own life, are real, well-documented, and increasingly well-understood. The neuroscience behind dissociation now shows these processes in measurable neurobiological terms. The science is catching up, even if systems and services have sometimes been slower to follow.

Understanding where your experience sits on the dissociation spectrum, or reading about conditions like depersonalisation and derealisation, may help bring further clarity to what you are living with. You did not create this. You adapted, intelligently, to circumstances that were beyond your control.

When to Seek Help

Reading about the history of dissociation can sometimes bring your own experiences into sharper focus. If you are noticing symptoms such as dissociative episodes, gaps in memory, persistent feelings of depersonalisation or derealisation, or a fragmented sense of self, speaking with a mental health professional trained in trauma is an important step.

Look for therapists with training in trauma-focused approaches: EMDR (Eye Movement Desensitisation and Reprocessing), Somatic Experiencing, Internal Family Systems (IFS), or specialist trauma therapy. In the UK, your GP can be a starting point for a referral to NHS psychological therapies, or you can self-refer to an IAPT (Improving Access to Psychological Therapies) service in your area.

If you are in crisis or struggling with thoughts of self-harm, please do reach out to the services below.

Further Reading

Introductory: Herman, J. L. (1992). Trauma and Recovery. Basic Books. Accessible, compassionate, and essential for anyone affected by relational trauma. Van der Kolk, B. A. (2014). The Body Keeps the Score. Viking. A broad, readable exploration of trauma’s effects on brain, mind, and body.

Intermediate: Van der Hart, O., Nijenhuis, E. R. S., & Steele, K. (2006). The Haunted Self. W. W. Norton. The foundational text on structural dissociation theory; clinically detailed and deeply humane.

Accessible online resources: Mind (mind.org.uk) offers clear, UK-based information on dissociation and dissociative disorders. PODS (Positive Outcomes for Dissociative Survivors, pods-online.org.uk) is a specialist UK charity providing support and resources.

For practitioners and advanced readers: Nijenhuis, E. R. S., & Van der Hart, O. (2011). Dissociation in trauma: A new definition and comparison with previous formulations. Journal of Trauma & Dissociation, 12(4), 416–445. https://doi.org/10.1080/15299732.2011.570592

References

1. Charcot, J.-M. (1889). Clinical lectures on diseases of the nervous system (Vol. 3, T. Savill, Trans.). New Sydenham Society.
2. Janet, P. (1889). L’automatisme psychologique. Félix Alcan.
3. Breuer, J., & Freud, S. (1895). Studies on hysteria (J. Strachey, Trans.). Basic Books.
4. Ellenberger, H. F. (1970). The discovery of the unconscious: The history and evolution of dynamic psychiatry. Basic Books.
5. Ellenberger, H. F. (1970). The discovery of the unconscious: The history and evolution of dynamic psychiatry. Basic Books.
6. American Psychiatric Association. (1980). Diagnostic and statistical manual of mental disorders (3rd ed.). APA.
7. Herman, J. L. (1992). Trauma and recovery: The aftermath of violence. Basic Books.
8. American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). APA.
9. Loftus, E. F. (1993). The reality of repressed memories. American Psychologist, 48(5), 518–537. https://doi.org/10.1037/0003-066X.48.5.518
10. Van der Hart, O., Nijenhuis, E. R. S., & Steele, K. (2006). The haunted self: Structural dissociation and the treatment of chronic traumatization. W. W. Norton.
11. Nijenhuis, E. R. S., & Van der Hart, O. (2011). Dissociation in trauma: A new definition and comparison with previous formulations. Journal of Trauma & Dissociation, 12(4), 416–445. https://doi.org/10.1080/15299732.2011.570592
12. Van der Kolk, B. A. (2014). The body keeps the score: Brain, mind, and body in the healing of trauma. Viking.
13. Spiegel, D., Lewis-Fernández, R., Lanius, R., Vermetten, E., Simeon, D., & Friedman, M. (2013). Dissociative disorders in DSM-5. Annual Review of Clinical Psychology, 9, 299–326. https://doi.org/10.1146/annurev-clinpsy-050212-185531
14. World Health Organization. (2019). International classification of diseases (11th rev.). https://icd.who.int/