Trauma can change the way we experience the world.
Sometimes, after something frightening or overwhelming happens, we eventually find that life begins to feel safe again. The memories remain, but they become memories rather than something that feels as though it is happening right now.
For some people, however, the experience doesn't settle so easily.
A sound, smell, place, relationship or even a particular thought can suddenly transport someone back to what happened. Their body may react before their mind has had time to understand why. They might feel constantly on guard, avoid certain places or conversations, struggle to sleep, experience nightmares or feel disconnected from themselves and others.
This is where Post-Traumatic Stress Disorder (PTSD) comes in.
But what happens when trauma has been repeated, prolonged or interpersonal, particularly when it occurs in circumstances where escape feels impossible?
For some people, the effects can reach beyond the more familiar symptoms of PTSD and affect their emotional regulation, sense of identity and relationships.
This is often described as Complex Post-Traumatic Stress Disorder (CPTSD).
Although PTSD and CPTSD overlap considerably, understanding the distinction can help us appreciate why some people's trauma responses can feel particularly deep and pervasive.
First, what exactly is trauma?
Before talking about PTSD, it is helpful to understand trauma itself.
Trauma isn't simply determined by whether something was objectively "bad enough." Two people can experience similar events and respond very differently.
Trauma refers to the psychological impact of an event or series of events that overwhelms a person's ability to cope or creates an experience of extreme threat, helplessness or horror.
Traumatic experiences can include things such as:
- serious accidents
- physical or sexual assault
- childhood abuse
- domestic violence
- war and combat
- torture
- serious illness or medical trauma
- natural disasters
- witnessing violence
- sudden or traumatic bereavement
- captivity
- exploitation
- repeated interpersonal violence.
Importantly, trauma doesn't always produce PTSD.
A person can experience something deeply frightening and gradually recover without developing a trauma-related disorder.
Others may develop significant symptoms that persist and interfere with everyday life.
And sometimes, the effects of trauma don't look like what we traditionally imagine PTSD to look like.
Someone might not talk about nightmares or flashbacks at all.
Instead, they may say:
"I just don't feel like myself anymore."
"I don't trust anyone."
"I know I'm safe, but my body doesn't seem to believe it."
"I feel numb most of the time."
"I keep choosing relationships that hurt me."
"I don't know who I am without the trauma."
These experiences can be particularly important when considering CPTSD.
What is PTSD?
Post-Traumatic Stress Disorder is a psychological disorder that can develop following exposure to a traumatic or extremely threatening event or series of events.
The ICD-11 conceptualises PTSD around three central groups of symptoms:
1. Re-experiencing
The trauma can feel as though it is happening again in the present.
This might include:
- intrusive memories
- nightmares
- flashbacks
- intense emotional reactions to reminders
- physical sensations associated with the traumatic experience.
A flashback isn't necessarily like watching a complete film of the past.
Sometimes it is much more subtle.
A person may suddenly experience the smell of something associated with the trauma. Their heart begins racing. They feel frightened. They don't immediately understand why.
Their nervous system has essentially detected danger before their conscious mind has caught up.
2. Avoidance
After trauma, people often try to protect themselves by avoiding reminders.
They might avoid:
- particular places
- people
- conversations
- news reports
- photographs
- relationships
- driving
- travelling
- intimacy
- thoughts or feelings connected with the trauma.
Avoidance can provide short-term relief.
"If I don't think about it, I don't have to feel it."
The difficulty is that extensive avoidance can gradually make the world smaller.
Someone may stop going out.
Then stop seeing friends.
Then stop travelling.
Then stop talking about what happened.
Eventually, their life can become organised around avoiding anything that might trigger the trauma.
3. A persistent sense of current threat
PTSD can also leave the nervous system stuck in a state of heightened alertness.
A person might:
- constantly scan their environment
- startle easily
- feel unable to relax
- experience irritability or anger
- have difficulty sleeping
- feel constantly unsafe
- struggle to concentrate
- experience strong physical anxiety responses.
Imagine having a smoke alarm that has become extremely sensitive.
A little steam from the shower might be enough to trigger it.
Similarly, after trauma, the brain and body can become highly sensitive to potential signs of danger.
The problem isn't that the person is deliberately "overreacting."
Their threat-detection system has learned that danger can happen.
PTSD isn't "just being unable to get over something"
This is an important distinction.
People sometimes say things like:
"It happened years ago. Why haven't they moved on?"
But trauma isn't simply about remembering something unpleasant.
Trauma can alter how a person experiences safety, memory, emotions and threat.
The person may understand intellectually that the danger has passed while their nervous system continues responding as though it hasn't.
This is why telling someone with PTSD to "just forget about it" is unlikely to help.
The problem isn't that they haven't tried hard enough.
So, what is Complex PTSD?
Complex Post-Traumatic Stress Disorder (CPTSD) includes the core symptoms of PTSD but also involves broader and more persistent difficulties in how a person regulates emotions, experiences themselves and relates to other people.
CPTSD is recognised as a separate diagnosis in the ICD-11, used internationally.
The DSM-5-TR, used widely in the United States, does not have a separate CPTSD diagnosis. Instead, some of the difficulties associated with what is often called CPTSD are incorporated within PTSD and related clinical presentations.
This difference between diagnostic systems is important.
It means that when clinicians talk about CPTSD, they may not necessarily be using exactly the same diagnostic framework.
PTSD and CPTSD: what is the difference?
The easiest way to understand CPTSD is to think of it as:
PTSD + disturbances in self-organisation.
In ICD-11, CPTSD requires the PTSD symptoms described above, alongside three additional areas of difficulty:
1. Difficulties with emotional regulation
A person may find emotions extremely difficult to manage.
They might experience:
- intense anger
- overwhelming anxiety
- emotional flooding
- difficulty calming themselves
- emotional numbness
- feeling shut down
- dissociation
- difficulty understanding or tolerating emotions.
Sometimes people with CPTSD describe feeling as though they have only two settings:
completely overwhelmed or completely numb.
There can seem to be very little emotional middle ground.
2. A persistent negative sense of self
This can be one of the most painful aspects of complex trauma.
A person may not simply think:
"Something terrible happened to me."
Instead, they may come to believe:
"There is something terrible about me."
They might experience:
- deep shame
- worthlessness
- guilt
- feeling defective
- feeling permanently damaged
- feeling defeated
- believing they are fundamentally different from other people.
This distinction is incredibly important.
PTSD can make someone feel unsafe in the world.
CPTSD can also make someone feel unsafe within themselves.
The person may carry the trauma into their identity.
Instead of:
"Someone hurt me,"
the internal story can become:
"I am someone who deserves to be hurt."
That belief can have profound consequences for relationships, boundaries and self-worth.
3. Difficulties in relationships
Complex trauma can also affect a person's ability to connect with others.
They may:
- struggle to trust people
- fear abandonment
- become highly sensitive to rejection
- struggle with emotional intimacy
- feel disconnected from others
- avoid relationships altogether
- become excessively dependent on others
- find it difficult to maintain stable relationships
- expect others to eventually hurt or leave them.
Sometimes the person desperately wants closeness while simultaneously fearing it.
They might think:
"I desperately want someone to love me, but I don't feel safe letting anyone close."
This can create painful patterns in relationships.
The person may move towards someone and then withdraw.
They may constantly look for signs that someone is angry.
They may interpret distance as rejection.
Or they may tolerate unhealthy relationships because being alone feels even more frightening.
Does CPTSD only happen after childhood trauma?
This is a common misconception.
Prolonged and repeated interpersonal trauma, particularly trauma occurring early in life, is associated with a greater likelihood of CPTSD.
Examples can include:
- prolonged childhood abuse
- repeated sexual abuse
- chronic domestic violence
- captivity
- torture
- prolonged exploitation.
However, the ICD-11 does not require a particular type of trauma for CPTSD.
Research suggests that CPTSD can occur following different forms of trauma, although prolonged and repeated interpersonal trauma is particularly associated with it.
So we shouldn't assume:
"They experienced one traumatic event, therefore it can't be CPTSD."
Nor should we assume:
"They experienced childhood trauma, therefore they must have CPTSD."
The symptoms and their impact on the person's functioning are what matter.
The body remembers what the mind tries to forget
One of the most interesting aspects of trauma is that trauma responses aren't purely psychological.
They can be profoundly physical.
Someone may experience:
- racing heart
- sweating
- shaking
- nausea
- muscle tension
- headaches
- sleep disturbance
- panic
- gastrointestinal symptoms
- an exaggerated startle response.
A person might know:
"I'm safe."
Yet their body responds:
"No, we're not."
This can be incredibly confusing.
And when someone repeatedly experiences physical symptoms without understanding their connection to trauma, they may begin to fear their own body.
Fight, flight, freeze and fawn
We often hear about the fight-or-flight response, but trauma responses can be more varied.
Fight
The person may respond to perceived danger with anger, confrontation or aggression.
Flight
They may escape, avoid, leave or constantly keep themselves busy.
Freeze
They may feel paralysed, numb or unable to act.
Fawn
Some trauma survivors respond by becoming highly accommodating.
They may:
- struggle to say no
- constantly please others
- suppress their own needs
- avoid conflict
- apologise excessively
- take responsibility for other people's emotions.
For someone who grew up learning that keeping another person's mood stable was necessary for safety, people-pleasing can become an automatic survival strategy.
Later in life, however, the same strategy may make it difficult to establish healthy boundaries.
Dissociation and trauma
Dissociation can also occur in trauma-related conditions.
Dissociation can involve feeling:
- detached from yourself
- emotionally numb
- disconnected from your surroundings
- as though you are observing yourself from outside your body
- as though the world doesn't feel completely real.
For some people, dissociation becomes a way of psychologically distancing themselves from experiences that feel unbearable.
It can be understood as a protective response.
But something that may have helped a person survive an overwhelming situation can later interfere with everyday life.
Why do traumatic memories feel different?
Ordinary memories tend to become integrated into our autobiographical story.
We can say:
"That happened to me last year."
We understand that it happened in the past.
Traumatic memories can sometimes behave differently.
A reminder can trigger sensations, emotions and images that feel immediate.
Instead of:
"That happened then."
the nervous system responds as though:
"It's happening now."
This helps explain why someone can logically know that they are safe while simultaneously experiencing intense fear.
Why do some people develop PTSD and others don't?
There isn't one simple explanation.
A person's response to trauma can be influenced by many factors, including:
- the nature and severity of the trauma
- whether the trauma was repeated
- whether the person could escape
- previous traumatic experiences
- childhood experiences
- social support
- coping strategies
- ongoing stress
- the person's interpretation of what happened
- whether they remain in an unsafe environment.
And perhaps most importantly, people respond differently to trauma.
There is no moral failing in developing PTSD.
It doesn't mean someone is weak.
And recovering from trauma doesn't mean someone is stronger than the person who hasn't recovered.
Trauma responses are not character tests.
PTSD and CPTSD can affect relationships
Trauma doesn't stay neatly inside the individual.
It can enter relationships.
Someone who has experienced betrayal may struggle to trust a loving partner.
Someone who has experienced abandonment may become highly sensitive to distance.
Someone who has experienced controlling relationships may interpret ordinary requests as attempts to control them.
Someone who has experienced abuse may have difficulty recognising what a healthy relationship actually feels like.
And someone who has learned that love and danger can coexist may unconsciously find familiar relationship dynamics more comfortable than healthy ones.
This is one reason trauma-informed therapy needs to be compassionate rather than judgmental.
A behaviour that looks confusing from the outside may have made perfect sense in the context of the person's history.
"Why didn't they just leave?"
This question is often asked about people who experience prolonged abuse.
But leaving an unsafe situation is not always simple.
A person may be financially dependent.
They may have children.
They may fear retaliation.
They may have nowhere to go.
They may have been systematically isolated.
They may believe they cannot survive without the person.
Or they may have become conditioned to minimise danger.
And in childhood, a child may literally have no ability to leave.
This is one reason why understanding trauma requires us to look beyond behaviour and consider context.
Treatment for PTSD
The good news is that PTSD is treatable.
In the UK, NICE recommends trauma-focused psychological interventions for adults with PTSD, including trauma-focused CBT approaches. EMDR is also recommended for adults with PTSD in appropriate circumstances.
Trauma-focused CBT can include approaches such as:
- Cognitive Processing Therapy
- Cognitive Therapy for PTSD
- Prolonged Exposure
- Narrative Exposure Therapy.
Treatment generally involves helping the person understand their trauma responses, process traumatic memories and meanings, reduce avoidance and rebuild functioning.
EMDR is another evidence-based approach used for PTSD. NICE recommends that it is delivered by appropriately trained practitioners and includes preparation, management of distressing memories and processing of trauma-related material.
What about CPTSD?
Treatment for CPTSD can be more complex because the difficulties extend beyond the traumatic memories themselves.
A person may need support with:
- emotional regulation
- grounding
- managing dissociation
- developing a sense of safety
- self-compassion
- shame
- interpersonal boundaries
- relationships
- identity
- trauma processing.
There has historically been considerable interest in phase-based approaches to complex trauma.
These commonly involve:
Phase 1: Safety and stabilisation
Developing skills to regulate emotions, tolerate distress, manage dissociation and establish safety.
Phase 2: Trauma processing
When the person has sufficient stability and resources, traumatic memories and meanings can be processed.
Phase 3: Integration and reconnection
The focus shifts towards relationships, identity, meaningful activities, goals and building a life that is not organised around trauma.
However, it is important not to assume that every person with CPTSD requires exactly the same treatment sequence. The evidence base for ICD-11 CPTSD-specific treatment is still developing.
Treatment should therefore be individualised.
Healing isn't about erasing the past
One of the most important things we can communicate to someone recovering from trauma is that healing doesn't necessarily mean forgetting.
The goal isn't:
"I want to make sure I never think about what happened again."
It may be closer to:
"I can remember what happened without feeling as though I'm back there."
The trauma becomes part of the person's history rather than something that continually dictates their present.
From survival to living
Perhaps one of the most meaningful ways to understand recovery is the movement from survival to living.
For a person who has spent years scanning for danger, learning to feel safe can be a huge process.
For someone who has spent years believing they are unworthy, learning to treat themselves with compassion can feel unfamiliar.
For someone who has learned that relationships are dangerous, experiencing safe connection may initially feel uncomfortable rather than comforting.
This is why recovery can sometimes feel strange.
The person isn't simply learning new skills.
They may be learning a completely different way of experiencing themselves and the world.
A final thought
PTSD and CPTSD remind us that the effects of trauma are not always visible.
Someone can look perfectly fine while internally fighting intrusive memories, shame, hypervigilance, emotional overwhelm or profound disconnection.
They may go to work.
They may laugh with friends.
They may raise children.
They may appear successful.
And yet, internally, they may still be trying to convince their nervous system that the danger is over.
So perhaps instead of asking:
"Why can't you just move on?"
a more compassionate question is:
"What happened to you, and what does your mind and body need in order to feel safe again?"
Trauma may become part of someone's story.
But it does not have to become the whole story.
Recovery isn't about pretending that the trauma never happened.
It's about helping the person discover that what happened to them does not have to determine everything that happens next.
References
American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders (5th ed., text rev.; DSM-5-TR). American Psychiatric Association.
Brewin, C. R., Cloitre, M., Hyland, P., Shevlin, M., Maercker, A., Bryant, R. A., Humayun, A., Jones, L. M., Kagee, A., Rousseau, C., Somasundaram, D., Suzuki, Y., Wessely, S., van Ommeren, M., & Reed, G. M. (2017). A review of current evidence regarding the ICD-11 proposals for diagnosing PTSD and complex PTSD. Clinical Psychology Review, 58, 1–15.
National Institute for Health and Care Excellence. (2018). Post-traumatic stress disorder (NG116). NICE.
National Center for PTSD. (2026). Complex PTSD: History and Definitions. U.S. Department of Veterans Affairs.
National Center for PTSD. (2026). Complex PTSD: Assessment and Treatment. U.S. Department of Veterans Affairs.
World Health Organization. (2019). International Classification of Diseases for Mortality and Morbidity Statistics, 11th Revision (ICD-11). World Health Organization.
World Health Organization. (2024). Clinical descriptions and diagnostic requirements for ICD-11 mental, behavioural and neurodevelopmental disorders. World Health Organization.