Noradrenergic PTSD hyperarousal — MRCPsych Paper A MCQ

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ModerateNeurophysiology and neurochemistryNoradrenergic PTSD hyperarousalMRCPsych Paper A

A 30-year-old woman develops post-traumatic stress disorder after an assault. She experiences recurrent trauma-related nightmares, marked hypervigilance and an exaggerated startle response. Which neurochemical alteration is most strongly associated with this hyperarousal symptom cluster?

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Correct answer: B — Increased locus coeruleus noradrenergic transmission

The correct answer is B. PTSD hyperarousal is associated with increased activity and stress responsivity of the central noradrenergic system, particularly locus coeruleus projections. Excess noradrenergic signalling promotes heightened alertness, autonomic arousal, sleep disruption, hypervigilance and exaggerated startle. Mesolimbic dopamine is more closely associated with reward, motivational salience and psychotic symptoms. Serotonergic dysfunction may contribute broadly to anxiety and mood symptoms but is not the principal neurochemical correlate of this hyperarousal cluster. Reduced basal forebrain acetylcholine is classically associated with cognitive impairment, particularly in neurodegenerative disorders. Increased GABAergic inhibition within the amygdala would tend to suppress fear-related neuronal output rather than produce persistent arousal.

Reference: Hendrickson RC, Raskind MA. Noradrenergic dysregulation in the pathophysiology of PTSD. Experimental Neurology. 2016;284:181–195. https://pubmed.ncbi.nlm.nih.gov/27222130/