Complex trauma

The UK Trauma Council defines complex trauma as traumatic experiences involving multiple events with interpersonal threats during childhood or adolescence.

Such events may include abuse, neglect, interpersonal violence, community violence, racism, discrimination, and war.

These experiences have several key features. First, they typically arise within the context of a child’s relationships. Second, they occur during child development, with important implications for their potential impact. Finally, they are chronic or repeated.

The impact of complex trauma

Exposure to complex trauma can impact a child’s emotional, psychological, social, and physical development. But, not all children are affected in the same way. Reactions can range from immediate and severe to limited or no adverse reaction. And for some, the impact is delayed. Genetic, biological, psychological, and social factors as well as the nature of trauma itself can influence the reaction. It is helpful to remember that the child’s experience of an event is different from their response to the event.

The experience of complex trauma can impact multiple aspects of child development at the biological level and in psychological and emotional functioning [3]. Changes may occur in:

  • brain structure and function
  • levels of cortisol and levels of inflammation
  • how a child identifies, responds to and regulates their emotions
  • how a child develops their sense of self, their self-worth, and their sense of others – particularly in relation to trust.

However, not all children and young people who experience complex trauma go on to develop mental health (or indeed social) problems. Protective influences play an important role in determining outcome.

Mental health outcomes

Complex trauma typically has a more significant impact on children and young people’s mental health outcomes than non-complex forms of trauma. However, the outcomes following experiences of complex trauma vary significantly.

Mental health disorders commonly associated with complex trauma include [4]:

  • anxiety
  • depression
  • post-traumatic stress disorder (PTSD)
  • complex post-traumatic stress disorder (Complex PTSD)
  • conduct disorder.

Children can also present with many different responses at the behavioural level, such as increased risk of self-harm, suicide, and poorer educational attainment. There is also evidence of an impact on physical health [3].

Different approaches in how complex trauma is measured have been shown to capture different groups of individuals characterised by different patterns of mental and physical health outcomes.

Considering these effects, it is unsurprising that there can be a significant impact on a child’s social functioning. Increased difficulties are often observed in their relationships with peers and adults. But again, not all children will show all or any of these effects. However, it is very likely that exposure to complex trauma will impact at least one or more of these aspects of development for most children to some degree.

How common is complex trauma?

There is good evidence that complex trauma affects a significant minority of children in the UK. A community study by the National Society for the Prevention of Cruelty to Children (NSPCC) found that nearly 1 in 5 children (18.6%) experience some form of abuse or neglect [1]. Abuse and neglect are commonly described as complex traumas although not all cases will reach a definitional threshold.

However, the prevalence of children and young people with complex trauma experiences varies depending on how it is measured and defined.

There are many different approaches to measuring complex trauma experiences – asking children directly, asking parents, and relying on statutory records (e.g. from social services or police). There are also many different definitions of what constitutes complex trauma. Different methods – as well as the different ways that complex trauma can be defined – will significantly influence the prevalence estimate [2].

Complex trauma and Complex PTSD

Complex Post Traumatic Stress Disorder, or Complex PTSD, is a formal diagnosis of a mental health disorder. Complex trauma is a series of events and processes, not a diagnosis. Experiencing complex trauma does not mean that an individual will develop Complex PTSD.

Complex PTSD is a relatively new diagnosis and was developed to reflect the fact that some individuals present with additional symptoms following trauma not captured with a traditional PTSD diagnosis. These can include:

  • difficulties regulating emotions
  • feelings of shame or guilt
  • experiencing intense feeling of loneliness
  • risky or destructive behaviour
  • significant difficulties in building and maintaining relationships with others [7].

Complex PTSD may be diagnosed in adults or children who have experienced traumatic events, such as violence, neglect, or abuse. However, many individuals who experience complex trauma do not develop Complex PTSD. Complex trauma can also cause other disorders, such as anxiety and depression. There is an ongoing debate about the most suitable interventions for Complex PTSD in children [8], [10].

What helps with complex trauma?

The UK Trauma Council has developed nine principles informed by an understanding of complex trauma, its effect on child development, and evidence-based responses that care givers, professionals and services can engage in to address the impacts of complex trauma.


  1. Establishing a common definition of complex trauma
  2. Promoting and stabilising trusted relationships
  3. Cultivating supportive interactions
  4. Actively enabling young people’s agency
  5. Recognising adaptations and building social connections
  6. Holistically responding to multiple needs
  7. Providing evidence-based interventions
  8. Tackling contextuality and systemic factors
  9. Supporting the workforce

For more information on these evidence-based principles, please read Complex trauma: evidence-based principles for the reform of children’s social care.

Professional responses to complex trauma

How professionals seek to help children following complex trauma can be understood as falling into two categories: prevention and mitigation [3].

The first response seeks to prevent the recurrence of exposure. For example, statutory agencies may provide an intervention to improve family functioning. Or, they may decide on the basis of a risk assessment to remove a child from their home and place them in an alternative safe environment.

The second response is to seek to mitigate the potential impact of complex trauma. This encompasses a broad range of responses, given the range of potential difficulties. For example, Trauma-Focused Cognitive Behavioural Therapy, if a child presents with PTSD. By contrast, a child presenting with depression symptoms may receive CBT, psychodynamic psychotherapy or family therapy. A child presenting with behavioural difficulties at school but no mental health problems, may benefit from a systemic intervention involving the child, carers, and teachers. In other words, any response should be formulated on the basis of a child’s individual presentation.


There remain many gaps in evidence as to what constitutes the most effective form of help for children who have experienced complex trauma. Moreover, we lack an evidence-based model of preventative help that reduces the risk of mental health problems emerging across development following trauma exposure [9].

If you are looking for training on areas related to complex trauma, join one of our upcoming live Insight Series webinars providing expert insights into important issues affecting children and young people. Find out more here.


  1. Radford, L. et al. (2011) Child Abuse and Neglect in UK Today. NSPCC, London. (PDF)
  2. Baldwin, J. R., Reuben, A., Newbury, J. B., & Danese, A. (2019). Agreement between prospective and retrospective measures of childhood maltreatment: a systematic review and meta-analysis.  JAMA Psychiatry76(6), 584-593.
  3. Danese, A., & McCrory, E. (2015). Child maltreatment. Rutter’s Child and Adolescent Psychiatry, 364–375.
  4. Lewis, S.J., Arseneault, L., Caspi, A., Fisher, H.L., Matthews, T., Moffitt, T.E., Odgers, C.L., Stahl, D., Jia Ying Teng, & Danese, A. (2019). The epidemiology of trauma and post-traumatic stress disorder in a representative cohort of young people in England and Wales. The Lancet Psychiatry, 6(3), 247–256.
  5. Danese, A. (2019). Annual Research Review: Rethinking childhood trauma‐new research directions for measurement, study design and analytical strategies. Journal of Child Psychology and Psychiatry, 61(3), 236–250.
  6. Danese, A., & Widom, C. S. (2020). Objective and subjective experiences of child maltreatment and their relationships with psychopathology. Nature Human Behaviour, 4(8), 811–818.
  7. Wamser‐Nanney, R., & Vandenberg, B. R. (2013). Empirical support for the definition of a complex trauma event in children and adolescents. Journal of Traumatic Stress26(6), 671-678.
  8. Hiller, R. M., Meiser‐Stedman, R., Elliott, E., Banting, R., & Halligan, S. L. (2020). A longitudinal study of cognitive predictors of (complex) post‐traumatic stress in young people in out‐of‐home care. Journal of Child Psychology and Psychiatry, 62(1), 48–57.
  9. McCrory, E., Gerin, M., & Viding, E. (2017). Annual Research Review: Childhood maltreatment, latent vulnerability and the shift to preventative psychiatry – the contribution of functional brain imaging. Journal of Child Psychology and Psychiatry, 338-357.
  10. Heide, F. J. J. T., Mooren, T. M., & Kleber, R. J. (2016). Complex PTSD and phased treatment in refugees: A debate piece. European Journal of Psychotraumatology7(1), 28687.
Decor Decor Decor Decor Decor Decor Decor Decor