Impaired fear inhibition is a biomarker of PTSD but not depression.
BACKGROUND
A central problem in posttraumatic stress disorder (PTSD) is a reduced capacity to suppress fear under safe conditions. Previously, we have shown that combat-related PTSD patients have impaired inhibition of fear-potentiated startle (FPS). Given the high comorbidity between PTSD and depression, our goal was to see whether this impairment is specific to PTSD, or a non-specific symptom associated with both disorders.


METHODS
Fear-potentiated startle was assessed in 106 trauma-exposed individuals divided into four groups: (a) No diagnosis control, (b) PTSD only, (c) major depression (MDD) only, and (d) comorbid PTSD and MDD. We used a novel conditional discrimination procedure, in which one set of shapes (the danger signal) was paired with aversive airblasts to the throat, and different shapes (the safety signal) were presented without airblasts. The paradigm also included fear inhibition transfer test.


RESULTS
Subjects with comorbid MDD and PTSD had higher FPS to the safety signal and to the transfer test compared to controls and MDD only subjects. In contrast to the control and MDD groups, the PTSD and comorbid PTSD and MDD groups did not show fear inhibition to safety cues.


CONCLUSIONS
These results suggest that impaired fear inhibition may be a specific biomarker of PTSD symptoms.
Jovanovic
Tanja
T
Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, 49 Jesse Hill Jr. Drive, Atlanta, GA 30303, USA.tjovano@emory.edu
Norrholm
Seth D
SD
Blanding
Nineequa Q
NQ
Davis
Michael
M
Duncan
Erica
E
Bradley
Bekh
B
Ressler
Kerry J
KJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D001143:Arousal; D015415:Biomarkers; D015897:Comorbidity; D003866:Depressive Disorder / Q000453:epidemiology / Q000503:physiopathology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D004576:Electromyography; D005239:Fear; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D008875:Middle Aged; D013216:Reflex, Startle; D013313:Stress Disorders, Post-Traumatic / Q000453:epidemiology / Q000503:physiopathology* / Q000523:psychology*; D011795:Surveys and Questionnaires; D055815:Young Adult
D015415:Biomarkers