Key result
Occupation-related PTSD was associated with a non-significant 6.5–30% elevation in fronto-limbic TSPO binding compared to healthy controls (p=0.297), though binding was significantly higher in PTSD participants with frequent cannabis use.
Why the study?
The role of microglia in the pathophysiology of PTSD and neurobiological stress-regulating systems remains incompletely understood.
Does occupation-related PTSD increase TSPO binding (microglia activation) in fronto-limbic brain regions compared to healthy controls?
Case-Control (n=39)
No
Does occupation-related PTSD increase TSPO binding (microglia activation) in fronto-limbic brain regions compared to healthy controls?
Effect estimate: 6.5-30% higher
p-value: p=0.297
TSPO binding, a marker of microglia activation, was not significantly elevated in occupation-related PTSD overall, but may be increased in subgroups such as frequent cannabis users.
Does not support TSPO imaging for occupation-related PTSD; leaves open cannabis subgroup effects for prospective study.
Microglia are immune brain cells implicated in stress-related mental illnesses including posttraumatic stress disorder (PTSD). Their role in the pathophysiology of PTSD, and on neurobiological systems that regulate stress, is not completely understood. We tested the hypothesis that microglia activation, in fronto-limbic brain regions involved in PTSD, would be elevated in participants with occupation-related PTSD. We also explored the relationship between cortisol and microglia activation. Twenty participants with PTSD and 23 healthy controls (HC) completed positron emission tomography (PET) scanning of the 18-kDa translocator protein (TSPO), a putative biomarker of microglia activation using the probe [ 18 F]FEPPA, and blood samples for measurement of cortisol. [ 18 F]FEPPA V T was non-significantly elevated (6.5–30%) in fronto-limbic regions in PTSD participants. [ 18 F]FEPPA V T was significantly higher in PTSD participants reporting frequent cannabis use compared to PTSD non-users (44%, p = 0.047). Male participants with PTSD (21%, p = 0.094) and a history of early childhood trauma (33%, p = 0.116) had non-significantly higher [ 18 F]FEPPA V T . Average fronto-limbic [ 18 F]FEPPA V T was positively related to cortisol (r = 0.530, p = 0.028) in the PTSD group only. Although we did not find a significant abnormality in TSPO binding in PTSD, findings suggest microglial activation might have occurred in a subgroup who reported frequent cannabis use. The relationship between cortisol and TSPO binding suggests a potential link between hypothalamic–pituitary–adrenal-axis dysregulation and central immune response to trauma which warrants further study.
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Watling et al. (2023) conducted a case-control in Occupation-related posttraumatic stress disorder (PTSD) (n=39). Occupation-related PTSD vs. Healthy controls was evaluated on Fronto-limbic [18F]FEPPA VT (TSPO binding) (6.5-30% higher, p=0.297). Occupation-related PTSD was associated with a non-significant 6.5–30% elevation in fronto-limbic TSPO binding compared to healthy controls (p=0.297), though binding was significantly higher in PTSD participants with frequent cannabis use.
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