Basic Neurosciences · Paper A
Post-traumatic stress disorder features
Post-traumatic stress disorder is a memory that never received its date stamp, so the body keeps answering it as present danger. Three things follow from that one fault, and together they are the diagnosis: the event replays as if it were happening now (intrusive images, nightmares, flashbacks), the person builds a life around not triggering the replay (avoidance), and the alarm never stands down (hypervigilance, startle, broken sleep, or in ICD-11 wording a persistent sense of current threat). What does not follow from the fault is timing, and the two manuals set it differently: DSM-5 waits until symptoms have lasted more than a month, and ICD-11 asks for at least several weeks. And what is easy to forget is that most people exposed to a traumatic event never develop the disorder at all.
The cause is an event plus the way that event was stored, and the second half is the part worth understanding. A memory laid down under extreme fear is sensory-rich (smells, sounds, bodily sensations) and poorly connected to the ordinary autobiographical record that gives a memory its time and place. One recognised cognitive model of the disorder, from Ehlers and Clark (2000, Behaviour Research and Therapy), makes this the central fault: because the memory lacks context, any matching cue retrieves it with a quality of nowness, and the person appraises the intrusion as proof of continuing danger. Avoidance then does the maintaining work. Each time a reminder is escaped or a feeling numbed, the memory is spared the updating that would have taught it the danger is over, so the replay keeps its live quality. Who develops it is partly about the event and partly about the person. Interpersonal and repeated trauma (sexual assault, combat, torture, abuse in childhood) carry the highest conditional risk; a single road accident carries a lower one. Prior psychiatric illness, low social support, and dissociationA disconnection between a person's thoughts, feelings, memories, or sense of identity, often as a response to stress.Read more → at the time of the event raise risk. Women develop the disorder at roughly twice the rate of men after exposure: in the United States National Comorbidity Survey (Kessler and colleagues, 1995, Archives of General Psychiatry) lifetime prevalenceThe proportion of a population who have a condition at a given point or period in time.Read more → was 10.4 per cent in women and 5.0 per cent in men, 7.8 per cent overall. The classification followed the mechanism. DSM-5 (2013) moved the disorder out of the anxiety disorders into a trauma- and stressor-related chapter, and ICD-11 placed it among disorders specifically associated with stress, because the defining feature is a reaction to an identified event, not free-floating fear.
A woman who survived a house fire three years ago walks past a barbecue and, before she has registered the smoke, her heart is hammering and she is back in the hallway. She knows, a moment later, that she is in a park. The knowing comes second. That order, body first and calendar second, is post-traumatic stress disorder () in one scene, and you can read every feature of the disorder off it.
is a disorder that follows exposure to an event involving actual or threatened death, serious injury or sexual violence, in which the memory of that event keeps returning with the quality of happening now. ICD-11 requires three elements: re-experiencing in the present, deliberate avoidance of reminders, and a persistent sense of current threat (hypervigilance and exaggerated startle). DSM-5 describes the same picture in four clusters, adding negative changes in cognition and mood (numbing, detachment, persistent blame, inability to recall parts of the event). Both require the symptoms to impair functioning, but they set the clock differently: DSM-5 requires more than a month, and ICD-11 asks only that symptoms persist for at least several weeks.
Exposure is common; the disorder is not. Most people who live through a qualifying event recover in the weeks that follow without treatment, which is why NICE NG116 says to consider active monitoring for adults with subthreshold symptoms in the first month rather than intervention. The conditional risk depends on the event, and interpersonal, repeated and inescapable trauma (sexual assault, combat, torture, childhood abuse) carries far more risk than a single accident. Women develop at roughly twice the rate of men: in the United States National Comorbidity Survey (Kessler and colleagues, 1995), lifetime was 10.4 per cent in women and 5.0 per cent in men. When you read a stem, do not let the size of the event carry the diagnosis; let the replay carry it.
Picture a security guard whose ordinary job is to watch the live feed, stamp each clip with a date, and file it in the archive. One night a clip is recorded under such fear that it never gets its stamp. It stays on the live screen. Every time a passing shadow resembles it, the clip plays again, and the guard reacts as he would to a live intruder: sprinting to the door, sleeping badly, jumping at noises. Eventually he throws a cloth over the monitor. That brings relief, but a covered clip is still an unfiled clip, so nothing changes.
Every symptom maps onto that scene. The unstamped clip is the trauma memory, stored as sensory fragments (smell, sound, bodily sensation) without the autobiographical context that marks a memory as finished; this is the core of the cognitive model of Ehlers and Clark (2000), one recognised account of the disorder. The clip on the live screen is re-experiencing. The guard at the door is the persistent sense of current threat. The cloth is avoidance, and it is the maintaining factor, because the memory is never given the chance to learn the danger has passed.
The picture also tells you what treatment must do. Someone has to sit with the guard, watch the clip through, add the stamp, and file it. That is what trauma-focused cognitive behavioural therapy () and eye movement desensitisation and reprocessing (EMDR) do. Dimming the screen with a drug reduces the alarm without filing anything. Where the picture fails is timing: it suggests that replaying the clip in the first hours should help, and the evidence says the opposite, which you will meet again under management.
Work through a stem in the order the fault produces its effects. First, find the event and test it against the gate: death, serious injury or sexual violence, actual or threatened, experienced directly, witnessed, or learned about in a close relative. Second, look for nowness: intrusive images, nightmares, flashbacks in which the person acts or feels as if the event were recurring. Third, look for the alarm: startle, hypervigilance, irritability, insomnia, poor concentration. Fourth, look for the cloth: avoided routes, topics, people, and the emotional numbing that DSM-5 files under negative cognitions and mood and that ICD-11 left out of , keeping affective shut-down for complex PTSD.
Then read the clock, and notice which manual is running it. In DSM-5, symptoms within the first month, from day three onwards, are acute stress disorder; symptoms lasting more than a month are ; full criteria arriving six months or more after the event earn the delayed-expression specifier. ICD-11 asks only that symptoms persist for at least several weeks, and it has no acute stress disorder: its acute stress reaction is a normal response that settles within days and is not classed as a mental disorder.
Finally, ask about the trauma's shape: if it was prolonged and inescapable, for example captivity, domestic abuse or childhood abuse, and the stem adds affect dysregulation, a negative self-concept and broken relationships, you are looking at complex , which ICD-11 created as a sibling diagnosis and DSM-5 does not recognise.
The diagnosis is clinical. Confirm the qualifying event, establish re-experiencing, avoidance and threat, and date the onset and duration. Screening tools such as the Trauma Screening Questionnaire and the Checklist for DSM-5 (PCL-5) support but do not replace the assessment. Remember children: NG116 reminds you that re-experiencing in a young child can be repetitive play and frightening dreams without recognisable content, and that NG116 offers trauma-focused to children and young people from seven to seventeen, and says consider it at five and six, using the same core elements. Ask about (feeling detached from the body or from the world), which DSM-5 records as a specifier and which predicts a rougher course.
NG116 sets the order. For adults with , or clinically important symptoms presenting more than a month after the event, offer individual trauma-focused ; within the first month it is something to consider for acute stress disorder or clinically important symptoms. EMDR is an option for adults presenting more than three months after a non-combat trauma, or between one and three months if they prefer it. For children and young people, offer trauma-focused CBT; drug treatment is not offered under eighteen. In adults, consider venlafaxine or an such as sertraline if the person prefers a drug, and consider an antipsychotic such as risperidone alongside psychological therapy for disabling symptoms that have not responded to other treatment.
Two prohibitions carry the weight on a safety stem: do not offer psychologically focused debriefing to prevent or treat , and do not offer drugs, benzodiazepines included, to prevent it. Guidance last reviewed 6 September 2026.
Can you explain why a stem that describes a redundancy followed by tearfulness and insomnia is not , however miserable the person is? Can you explain why DSM-5 and ICD-11 no longer file PTSD with the anxiety disorders, and what ICD-11 added beside it? The answers are the event gate, the stress-related chapter, and complex PTSD.
A traumatic memory stored without its date stamp replays as present danger, the body answers with alarm and avoidance, and the treatment is to file the memory with therapy rather than dim it with a drug.