"What is developmental trauma?"

The clearest working definition is that developmental trauma is harm to the developing system, not just harm experienced by a child. The distinction matters. A frightening event in childhood, processed in safety, with caregivers able to help the child make sense of it, often does not produce developmental trauma. Conditions of ongoing unsafety, unpredictability, or relational disturbance during the period when the self, the body's regulation, and the template of relationship are being built, often do.

The territory is wider than abuse. Chronic neglect, exposure to caregivers who were themselves unregulated, witnessing violence in the home, sustained emotional unavailability, and serious early medical experiences without adequate regulating presence can all qualify. What is shared across the territory is that the harm intersects with development, not just with memory.

The International Classification of Diseases, Eleventh Revision (ICD-11) recognises Complex Posttraumatic Stress Disorder as a separate condition. The diagnostic shape includes the core PTSD symptoms (re-experiencing, avoidance, sense of current threat) plus three additional clusters that the ICD-11 calls "disturbances in self-organisation": difficulties in regulating affect, a persistent negative self-concept, and persistent disturbances in close relationships (Cloitre et al., 2018).

The Developmental Trauma Disorder framework, proposed by Cook and colleagues in 2005 and updated by Ford in 2023, names a similar pattern in children. The construct is not in the DSM-5 or ICD-11. It remains influential in the clinical literature even where the diagnosis itself is not formally adopted (Ford, 2023).

Three differences are most clinically relevant. The first is that the impact is on the regulatory and relational baseline, not on a discrete memory. The second is that interpersonal templates were learned during the period when the system was forming its expectations of safety and closeness, and those templates continue to apply rules that fit the original conditions. The third is that symptoms often look like personality, mood disorder, or treatment-resistant depression or anxiety, rather than like classic PTSD.

The Blue Knot Foundation, Australia's national centre of excellence for complex trauma, recommends a phased treatment approach: stabilisation and relational safety first, then memory and meaning work where appropriate, then integration (Kezelman & Stavropoulos, 2019). The sequence reflects a clinical mechanism. Attempts to process specific memories before the regulatory baseline is established typically destabilise the system.