2 Neuroscience2.7 Neural circuits
2.7.1.4 Aggression
1 min read1 figure
Written by Resident Doctor Committee · Published
Reactive and proactive aggression
Feature | Reactive (threat-related) | Proactive (instrumental) |
|---|---|---|
Trigger | Provocation, frustration, perceived danger | Pursuit of resources, status or control |
Arousal | Often high, with anger | Often lower |
Basis | Immediate defensive response | Expected reward or learned benefit |
The two patterns overlap and are neither diagnoses nor legal categories.
Brain circuits
Amygdala gives cues their learned threat significance, but it also responds to reward and novelty, so it is not specific to aggression.
Orbitofrontal and ventromedial prefrontal cortex weigh the consequences of an action, and inferior frontal networks inhibit responses.
Ventral striatum and dopamine reinforce aggression that ends an unwanted demand or gains status.
Serotonin and impulsive aggression
Low cerebrospinal fluid (CSF) 5-hydroxyindoleacetic acid (5-HIAA), the main serotonin metabolite, is the most consistently replicated biological marker of impulsive aggression.
Low CSF 5-HIAA is also linked to suicidal behaviour.
It is a group association that cannot predict an individual's violence and does not measure a single circuit.
Tryptophan depletion can alter aggressive responding, depending on baseline traits.
Psychiatric and neurological states
Mania, frontal injury, intoxication, withdrawal and delirium can impair appraisal or control. Most people with psychosis are not violent.
Limits of prediction
No marker, hormone level or gene variant identifies who will be violent, because group findings overlap and base rates are low. Assessment rests on current intent, history, means, substances, symptoms and protective factors.