The human fear-circuitry and fear-induced fainting in healthy individuals

Abstract

The Paleolithic-Threat hypothesis reviewed here posits that habitual efferent fainting can be traced back to fear-induced allelic polymorphisms that were selected into some genomes of anatomically, mitochondrially, and neurally modern humans (Homo sapiens sapiens) in the Mid-Paleolithic because of the survival advantage they conferred during periods of inescapable threat. We posit that during Mid-Paleolithic warfare an encounter with "a stranger holding a sharp object" was consistently associated with threat to life. A heritable hardwired or firm-wired (prepotentiated) predisposition to abruptly increase vagal tone and collapse flaccidly rather than freeze or attempt to flee or fight in response to an approaching sharp object, a minor injury, or the sight of blood, may have evolved as an alternative stress-induced fear-circuitry response. Such a stable (balanced) polymorphism for the hemodynamically "paradoxical" flaccid-immobility in response to these stimuli may have increased some non-combatants' chances of survival. This is consistent with the unusual age and sex pattern of fear-induced fainting. The Paleolithic-Threat hypothesis also predicts a link to various hypo-androgenic states (e. g. low dehydroxy-epiandrosterone-sulfate. We offer five predictions testable via epidemiological, clinical, and ethological/ primatological methods. The Paleolithic-Threat hypothesis has implications for research in the aftermath of man-made disasters, such as terrorism against civilians, a traumatic event in which this hypothesis predicts epidemics of fear-induced fainting.

Evolution of the human fear-circuitry and acute sociogenic pseudoneurological symptoms: The Neolithic balanced-polymorphism hypothesis

“…Nesse has pointed out that subsequent assortative mating may also play a role in amplifying polygenic transmission resulting in shifting the severity of these responses from the normative range into the clinical range (a similar argument can be made for oligogenic transmission). Similar perspectives were echoed by Bracha (in press, 2004), Bracha et al (2005a), Buss et al (1998), Marks (1987Marks ( , 1988, Klein (1993), Marks and Nesse (1997), Niculescu and Akiskal (2001), Perry and Pollard (1998), Perry et al (1995), and Stein and Bouwer (1997).…”

“…Implications for the taxonomy of fear-induced faintness in DSM-V As we have argued in two recent reviews (Bracha, 2004;Bracha et al, 2005a), blood-injection-injury phobia is a pseudo-neurocardiovascular disorder, which is physiologically puzzling and hemodynamically paradoxical when compared with all other anxiety disorders. We posit that blood-injection-injury fears are better conceptualized as part of a new DSM-V bDissociative-Conversive SpectrumQ because of shared features, which are all in the bfaintnessspectrumQ (fear-induced fainting, swooning, bmedically unexplained dizziness,Q and lightheadedness).…”

The origin of vasovagal syncope: to protect the heart or to escape predation?

“…According to the Conflict theory, the VVS evolved during the Paleolithic era only in the human lineage [9]. In situations of inter-group attacks and killing, loss of consciousness triggered by fear-circuitry activation might have conferred a survival advantage on non-combatants (particularly children and women) when threats were inescapable [9].…”

Utility of Fear Severity and Individual Resilience Scoring as a Surge Capacity, Triage Management Tool during Large-Scale, Bio-Event Disasters

“…These background concepts have been reviewed by Bracha. 19,[23][24][25][26] Building on concepts pioneered by Nesse, Bracha has argued that neuro-evolutionary timedepth principles also are useful in predicting human behaviors during the early stages of pandemics. 19,27 Intensive animal husbandry practices that facilitate re-assortmenttriggered genomic shifts and pandemics only appeared following the emergence of high-population-density societies (circa 2000 BC).…”