PTSD is associated with inflammation but the cause is unclear. What do you think?. Does neuroinflammation cause the symptoms of PTSD or does PTSD cause neuroinflammation and systemic inflammation?
The endocannabinoid system modulates inflammation via TLRs and there is endocannabinoid deficiency in PTSD. Plus, stress-induced leaky gut can also cause activation of TLRs. So mechanisms are going to be multiple.
An interesting question! It appears that people with an a priori altered neuroinflammatory sytem are at increased risk to experiencing PTSD a posteriori.
Mendoza C, Barreto GE, Ávila-Rodriguez M, Echeverria V.Role of neuroinflammation and sex hormones in war-related PTSD.Mol Cell Endocrinol.2016 Oct 15;434:266-77. doi: 10.1016/j.mce.2016.05.016.
Zass LJ, Hart SA, Seedat S, Hemmings SM, Malan-Müller S. Neuroinflammatory genes associated with post-traumatic stress disorder: implications for comorbidity.
Actually, not all children and adolescents with childhood adversity/trauma have an increased risk of PTSD. The magic word is "individual-environment-genetic-interaction". The following papers might give you further hints:
Belsky, J., Pasco Fearon, R.M., Bell, B., 2007. Parenting, attention and externalizing problems: testing mediation longitudinally, repeatedly and reciprocally. Journal of child psychology and psychiatry, and allied disciplines 48(12), 1233-1242.
Belsky, J., Steinberg, L., Draper, P., 1991. Childhood experience, interpersonal development, and reproductive strategy: and evolutionary theory of socialization. Child Dev 62(4), 647-670.
Quach, J.L., Nguyen, C.D., Williams, K.E., Sciberras, E., 2018. Bidirectional Associations Between Child Sleep Problems and Internalizing and Externalizing Difficulties From Preschool to Early Adolescence. JAMA Pediatr 172(2), e174363.
In my opinion, much of what has been identified as genetic markers for psychological distress are probably the result of epigenetic changes, not pure heredity.
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Your original question was, "Is PTSD caused by neuroinflammation or does PTSD cause neuroinflammation?" There is growing evidence that supports the view that inflammation is both a process and a signal. This signal is readily communicated between the periphery and the CNS, as with gut inflammation. When inflammation is induced within the CNS, in humans one commonly finds neurobehavioral changes.
An additional field of consideration that supports this occurrence is that of traumatic brain injury (TBI). Since TBI is still associated with an emotionally traumatic experience, the delineation between the physical and emotional factors is more of a gray matter than black and white. If someone is aware of an experimental model or clinical context in which neuroinflammation is clearly induced without associated emotional trauma, then your cause-and-effect question may find a resolute answer.