PTSD: symptoms, causes and treatment

Key points

• PTSD can follow a frightening or distressing event, though most people who experience trauma do not develop it. NICE puts the figure at 25% to 30% of those exposed [2][3].
• The four symptom clusters are re-experiencing, avoidance, hyperarousal, and negative changes in mood and thinking, often with dissociation [1].
• ICD-11, the system the NHS uses, lists complex PTSD separately, and DSM-5 does not [6].
• NICE recommends trauma-focused CBT and EMDR, and advises against debriefing after a traumatic event [2].

What PTSD is

Post-traumatic stress disorder (PTSD) is a mental health condition that can develop after a stressful, frightening or distressing event [3]. The memory does not settle into the past, returning as images or nightmares that feel as though the event is happening now [1].

If you need help now Do not wait for an appointment. Call Samaritans free on 116 123 at any hour, text SHOUT to 85258, or call NHS 111 and choose the mental health option. Call 999 if you or someone else is in immediate danger.

Most people who experience a traumatic event do not develop PTSD. NICE estimates that 25% to 30% of those exposed do, with much natural recovery in the first weeks [2]. In England, 5.7% of adults screened positive in 2023/4, rising to 11.4% at ages 16 to 24 [5].

Symptoms can begin straight after the event, or many months or even years later, though NICE describes delayed onset in fewer than 15% of cases [2][3].

Symptoms

NICE groups the symptoms of PTSD, including complex PTSD, into four clusters [1].

Re-experiencing

• Flashbacks, where part of the event feels as though it is happening now [1][3].
• Nightmares, and physical reactions to reminders [3].

Avoidance

• Staying away from people, places or conversations linked to what happened, keeping busy to avoid thinking about it, and gaps in memory [1][3].

Hyperarousal

• Feeling constantly alert for danger, called hypervigilance [1].
• Irritability, anger, startling easily, and poor sleep [1][3].

Negative changes in mood and thinking

• Feeling diminished, defeated or worthless, or guilt out of proportion to events [1].
• Low mood, and feeling distant from others [1][3].

Dissociation

Dissociation means feeling cut off from oneself or one’s surroundings, as though watching from outside the body. NICE lists it alongside emotional numbing [1].

PTSD is commonly confused with anxiety or depression, and complex PTSD with a personality disorder, because the difficulties with mood, self-image and relationships look similar from outside [6].

Types

ICD-11 recognises two separate trauma diagnoses: PTSD and complex PTSD [6].

• PTSD. Three core clusters: re-experiencing the event in the present, avoiding reminders, and a persistent sense of current threat [6].
• Complex PTSD. All the PTSD clusters plus lasting difficulties ICD-11 calls disturbances in self-organisation: trouble managing emotions, a persistently negative view of oneself, and difficulty in relationships [6]. It usually follows prolonged or repeated events that were hard to escape, such as childhood or domestic abuse [3][6].

Complex PTSD appears in ICD-11 but not in DSM-5, which covers these features within its broader PTSD criteria [6]. UK services classify using ICD-11, so a person can be given a complex PTSD diagnosis here that would not exist under the American system [6].

Causes and risk factors

Exposure to a traumatic event is the direct cause, but exposure alone does not explain who develops PTSD, and there is no reliable way to predict who will [2].

Events that can lead to PTSD include serious accidents, assault, abuse, violence, war, disasters, serious illness and a difficult birth, whether experienced directly, witnessed, or learned about [3][9].

Higher risk is linked to trauma that was prolonged or repeated, injury during the event, believing death was likely, little support afterwards, and an existing mental health condition [9].

One popular idea the evidence does not support is that talking an event through straight afterwards prevents PTSD. NICE recommends against psychologically focused debriefing [2].

How it is diagnosed

PTSD is diagnosed by a doctor or a qualified mental health professional, not by a questionnaire. NICE says GPs should take responsibility for assessment and initial coordination of care when someone presents in primary care with clinically important symptoms [2].

The assessment covers physical, psychological and social needs, and includes risk [2]. Expect questions about when symptoms began, their effect on daily life, sleep and mood, and any thoughts of self-harm, but nobody has to describe the event in detail at a first appointment.

Symptom checklists such as the PCL-C are screening tools, not diagnoses. The national survey counts people as screening positive, not diagnosed [5].

In England in 2024/25, 91.6% of people who completed a course of NHS Talking Therapies treatment had waited less than six weeks between referral and their first treatment session. That figure covers only people who finished treatment, so it excludes anyone still waiting or who dropped out [8].

A diagnosis names a recognised pattern and opens the door to specific treatments, but does not fix how long symptoms last.

Treatment

NICE guideline NG116 sets out an order of preference, with psychological treatment first [2].

In the first month after an event. NICE recommends considering active monitoring where symptoms fall below the diagnostic threshold, with follow-up within a month, and recommends against psychologically focused debriefing [2]. Where an adult has acute stress disorder or clinically important PTSD symptoms after trauma in the last month, NICE recommends offering individual trauma-focused CBT [2].

More than a month after. NICE recommends offering individual trauma-focused CBT to adults presenting more than a month after the event, typically over 8 to 12 sessions, and more where clinically indicated, such as after multiple traumas [2].

EMDR. Eye movement desensitisation and reprocessing uses guided eye movements while recalling the memory. NICE recommends considering it for non-combat-related trauma one to three months after the event, and offering it more than three months after, again over 8 to 12 sessions [2]. The evidence did not support it for combat-related trauma [2].

Complex presentations. For complex PTSD, NICE advises extra time to build trust by increasing the length or number of sessions [2]. The evidence here is thinner than for PTSD [7].

Medication. NICE does not recommend drug treatments to prevent PTSD in adults. Venlafaxine or an SSRI antidepressant can be considered where someone prefers medication, with regular review [2]. Antipsychotics are reserved for disabling symptoms that have not responded to other treatments, and are specialist-initiated [2].

Living with PTSD

Knowing your own triggers helps. Mind suggests noting the smells, sounds, words or places that set symptoms off, and planning ahead for those you cannot avoid [10].

Grounding techniques can shorten a flashback. Slow breathing while counting, naming what you can see and hear, or feeling the floor under your feet all anchor attention in the present [10].

Sleep is often the first thing to go. Keep a regular pattern, tell your GP if nightmares are frequent, and note when symptoms are worse, which gives a therapist something to work from [10].

Peer support groups put you in contact with people who recognise what you describe, and Combat Stress supports veterans and their families [4][10]. Telling an employer or university is your decision, and you do not need a diagnosis to ask for a change to hours or deadlines.

When to speak to a professional

If you need help now Call Samaritans free on 116 123 at any hour, text SHOUT to 85258, or call NHS 111 and choose the mental health option. Call 999 if you or someone else is in immediate danger.

Make a GP appointment if symptoms have lasted more than about a month, or are getting in the way of work, study, sleep or relationships. Go back if treatment you are already having is not helping [3].

Seek help sooner if you are using alcohol or drugs to cope, if flashbacks or dissociation are frequent enough to be unsafe, or if you are having thoughts of harming yourself or anyone else. Where someone is judged to be at risk, support can include a home treatment crisis team or a hospital stay [4].

If you are 18 or over, or 16 or over in some areas, you can refer yourself to an NHS talking therapies service without a GP referral [3].

Common questions

Does PTSD go away on its own?

Sometimes. NICE notes considerable natural recovery in the first weeks, which is why it recommends active monitoring rather than immediate therapy for mild symptoms in that month, and trauma-focused therapy when symptoms persist [2].

What is the difference between PTSD and complex PTSD?

Complex PTSD includes all the features of PTSD plus lasting difficulty managing emotions, a persistently negative view of oneself, and difficulty in relationships, usually after prolonged or repeated trauma that was hard to escape [3][6]. ICD-11 lists it separately, DSM-5 does not [6].

Can PTSD start years after the event?

Yes. The NHS says symptoms can appear straight after an event or many months or even years later [3]. NICE describes delayed onset in fewer than 15% of cases [2].

Clinical review pending

References

1. National Institute for Health and Care Excellence. Recommendations: Post-traumatic stress disorder. NICE guideline NG116, published 5 December 2018. https://www.nice.org.uk/guidance/ng116/chapter/Recommendations
2. National Institute for Health and Care Excellence. Post-traumatic stress disorder. NICE guideline NG116, full guideline text, published 5 December 2018. https://www.ncbi.nlm.nih.gov/books/NBK542453/
3. NHS. Post-traumatic stress disorder (PTSD). nhs.uk, page last reviewed 8 April 2026. https://www.nhs.uk/mental-health/conditions/post-traumatic-stress-disorder-ptsd/
4. NHS. Treatment: Post-traumatic stress disorder. nhs.uk, page last reviewed 8 April 2026. https://www.nhs.uk/mental-health/conditions/post-traumatic-stress-disorder-ptsd/treatment/
5. NHS England Digital. Adult Psychiatric Morbidity Survey: Survey of Mental Health and Wellbeing, England, 2023/4. Chapter 3: Posttraumatic stress disorder, published 27 November 2025. https://digital.nhs.uk/data-and-information/publications/statistical/adult-psychiatric-morbidity-survey/survey-of-mental-health-and-wellbeing-england-2023-24/posttraumatic-stress-disorder
6. Brewin CR. Complex post-traumatic stress disorder: a new diagnosis in ICD-11. BJPsych Advances, 2020, volume 26, issue 3, pages 145 to 152. https://www.cambridge.org/core/journals/bjpsych-advances/article/complex-posttraumatic-stress-disorder-a-new-diagnosis-in-icd11/2977140CBDAAF402610715BB609F688C
7. UK Trauma Council. Post-traumatic stress disorder (PTSD) and Complex PTSD. https://uktraumacouncil.org/trauma/ptsd-and-complex-ptsd
8. NHS England Digital. NHS Talking Therapies, for anxiety and depression, Annual reports, 2024-25, published 25 September 2025. https://digital.nhs.uk/data-and-information/publications/statistical/nhs-talking-therapies-for-anxiety-and-depression-annual-reports/2024-25
9. Mind. Causes of post-traumatic stress disorder (PTSD). mind.org.uk, published January 2026. https://www.mind.org.uk/information-support/types-of-mental-health-problems/post-traumatic-stress-disorder-ptsd-and-complex-ptsd/causes/
10. Mind. Self-care for PTSD. mind.org.uk, last updated January 2026. https://www.mind.org.uk/information-support/types-of-mental-health-problems/post-traumatic-stress-disorder-ptsd-and-complex-ptsd/self-care/