2 Neuroscience2.11 Integrated neurobiology of syndromes and states
2.11.5 Post traumatic stress disorders
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Written by Resident Doctor Committee · Published
Risk and course
Most people exposed to trauma do not develop PTSD.
Heritability is roughly 30 to 40%, with liability shared with anxiety and depression.
Childhood adversity, previous illness and lower premorbid cognitive ability raise the risk.
PTSD severity fluctuates over time after trauma, so a person's diagnostic status is not fixed and the course is not linear.
Courses include resilience, recovery, delayed symptoms and persistent distress, and one assessment cannot establish which will follow.
Circuitry of threat
Structure | Finding | What it produces |
|---|---|---|
Amygdala | Hyper-responsive to threat cues, poor habituation | Hypervigilance, exaggerated startle |
Hippocampus | Smaller volume, poor contextual processing | Fear regardless of the present setting |
Ventromedial prefrontal cortex | Reduced activity and amygdala connectivity | Failure of top-down inhibition and of extinction |
Small hippocampi partly precede trauma, because unexposed identical co-twins have comparably small hippocampi.
Noradrenaline and sleep
Noradrenergic over-activity disrupts REM sleep, which underlies the sleep disturbance and nightmares of PTSD.
The most consistent polysomnographic finding is increased REM density, with more stage N1 sleep and less slow-wave sleep.
Prazosin, an alpha-1 antagonist, lowers noradrenergic drive and helps nightmares by restoring continuous REM periods.
Complex PTSD
ICD-11 complex PTSD needs the full core PTSD picture plus three disturbances in self-organisation: affect dysregulation, a persistent negative self-concept and relationship difficulties.
It is linked to repeated interpersonal trauma in childhood, when stress regulation and attachment are still forming.
Maintaining processes
Avoidance brings short-term relief but blocks the corrective learning that trauma-focused therapies provide.