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Volume 14 No. 12
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Fear of Sleep May Be a Core Symptom of Sympathetic Activation and the Drive for Vigilance in Posttraumatic Stress Disorder

Madhulika A. Gupta, MD, MSc, FAASM, RST; Angelica D. Sheridan, BSc (Hon)
Department of Psychiatry, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada

A recent study by Kanady and colleagues1 examined the often underrecognized symptom of fear of sleep (FS) in posttraumatic stress disorder (PTSD) using the Fear of Sleep Inventory (FOSI) in 45 patients (20% veterans) with PTSD and insomnia. Patients were randomized to eight weekly sessions of cognitive behavioral therapy for insomnia (CBT-I) (n = 29) or a wait-list control group (n = 16). FS was not one of the treatment targets in the CBT-I protocol. PTSD was assessed with the Clinician Administered PTSD Scale for DSM-IV (CAPS). Some of the main findings were a direct correlation of pretreatment FS with overall PTSD severity (total CAPS score) (r = .40, P < .01), and CAPS hypervigilance intensity (r = .30, P = .04). FS did not correlate with pretreatment insomnia (measured by the Insomnia Severity Index [ISI]) but correlated with multiple sleep disturbances measured by the Pittsburgh Sleep Quality Index Addendum for PTSD. In the CBT-I group and not the control group, there was a reduction in FS, which correlated with a reduction in overall PTSD severity (r = .57, P < .01; versus r = −.14, P = NS in control patients) and hypervigilance (r = .43, P = .02; versus r = −.45, P = NS in controls). There was a reduction of FS following CBT-I even though FS was not a CBT-I treatment target. The authors observe that FS was related to complex non-sleep and sleep symptoms in PTSD and not simple insomnia.1

We have observed similar findings among 40 civilian PTSD patients (most of them survivors of sexual abuse and/or severe neglect) who completed the FOSI, PTSD Checklist for DSM-5 (PCL-5) and ISI, and underwent a level 3 home sleep apnea test (HSAT) (WatchPAT 200; Itamar Medical, Israel). FOSI scores were directly correlated with overall PTSD severity (total PCL-5 score) (r = .639, P < .001), PCL-5 symptom sub-scales (intrusive symptoms, avoidance, negative cognitions, hyperarousal) and the ISI (r = .548, P < .001). However, multiple regression analysis using FOSI score as dependent variable and all PCL5 subscales and ISI as independent variables revealed that only PCL-5 subscale for hyperarousal (β = .648, t = 4.959, P < .001) remained a significant predictor of FOSI in the regression model (adjusted R2 = .403). The FOSI correlated with several HSAT indices of hyperarousal, eg, number of wakenings/h (r = .353, P = .044).2

Our results support the findings of Kanady and colleagues that there is a significant correlation between FS and PTSD symptom severity. The correlation between FS and ISI no longer remained significant in the multiple regression model, where the PCL-5 hyperarousal subscale (which measures hypervigilance) alone accounted for the variance in FS, which further supports the results of Kanady et al. FS appears to be a core symptom of the underlying sympathetic activation and drive for vigilance in PTSD that may be associated with both non-sleep and sleep-related sympathetically mediated PTSD symptoms.


All authors have seen and approved the manuscript. The authors report no conflicts of interest.


Gupta MA, Sheridan AD. Fear of sleep may be a core symptom of sympathetic activation and the drive for vigilance in post-traumatic stress disorder. J Clin Sleep Med. 2018;14(12):2093.



Kanady JC, Talbot LS, Maguen S, et al. Cognitive behavioral therapy for insomnia reduces fear of sleep in individuals with posttraumatic stress disorder. J Clin Sleep Med. 2018;14(7):1193–1203. [PubMed Central][PubMed]


Gupta MA, Sheridan AD. Fear of sleep (FS) in posttraumatic stress disorder (PTSD) patients correlates directly with indices of hyperarousal during wakefulness and sleep. Sleep. 2018;41 Suppl 1:A348