Abstract:Aim: Despite being one of the most disabling symptoms of post-traumatic stress disorder (PTSD)—disrupting sleep continuity, reinforcing hyperarousal, and worsening psychiatric comorbidity—the physiological signature of Trauma-related nightmares (TRNs) under naturalistic sleep conditions remains poorly characterized. Methods: We used home-based, multi-sensor devices from the SOMMEPT cohort to assess whether TRNs display distinct autonomic dynamics before and after awakening. TRN awakenings were self-marked with the wristband button and validated through electroencephalography (EEG) inspection by a psychiatrist and a sleep physician. Each TRN event (N = 412) was matched 1:1 to three control conditions: spontaneous awakenings in 60 healthy military participants, awakenings in 34 military PTSD patients without TRNs, and non-nightmare awakenings from 74 military PTSD patients with TRNs. Pre-awakening autonomic activity was analyzed over 10 min, and post-awakening reactivity over a 2-min window using nonparametric statistics with cluster-based permutation correction. Results: TRNs were associated with heightened sudomotor activity and reduced vagal heart rate variability compared with spontaneous awakenings in healthy controls; differences were weaker versus PTSD patients without TRNs or non-TRN awakenings. Phasic Electrodermal activity (EDA) showed earlier peaks and prolonged recovery, while movement was lower before TRN-related awakenings. Post-awakening, TRNs elicited an abrupt surge: heart rate accelerated within ~40 s and normalized by ~2 min; tonic EDA remained elevated, phasic EDA bursts were longer, slower to recover, and motor activity rose during the first ~80 s. Conclusions: TRNs display a distinctive autonomic pattern with pre-awakening sudomotor buildup and post-awakening cardiovascular–electrodermal surges, supporting biomarker-based detection and targeted intervention. Trial registration: ClinicalTrials.gov Identifier: NCT04581850.