Wearables That See PTSD Coming: Circadian Instability After Mass Trauma

A new study published in Translational Psychiatry by Noa Magal, Ophir Netzer, Eden Eldar, Noga Mandelblit, Nitsan Sagi, Michal Oren, Roy Salomon and Roee Admon asks a question that could fundamentally change how we identify people at risk for PTSD: can the body's daily rhythms, measured passively in real life, predict who will struggle with chronic post-traumatic symptoms months later?

The team — based at the School of Psychological Sciences and the Integrated Brain and Behavior Research Center at the University of Haifa — built their study around a tragic natural experiment: the October 7th, 2023 terror attack on the Supernova music festival in Israel, where survivors witnessed life-threatening trauma at scale that has few precedents in the modern PTSD literature.

Study design

The researchers followed 211 survivors of the Supernova festival attack and a matched comparison group of 113 participants for a full month, three-to-six months post-event. Rather than bringing participants into a lab, they collected entirely real-world data using consumer-grade wearable sensors that continuously tracked:

• Sleep–wake patterns across days and nights
• Physical activity levels and timing
• Heart rate 24 hours a day

PTSD symptom severity was assessed with the Posttraumatic Checklist for DSM-5 (PCL-5) at three time points: before the recording month, immediately after, and again at follow-up eight-to-eleven months after the attack.

Quantifying circadian instability

To capture the stability of each participant's daily rhythms, the team computed two complementary indices. Behaviourally, they used the interday stability (IS) index of the sleep–wake cycle — how consistent a person's daily sleep pattern is from one day to the next. Physiologically, they fit cosinor models to each participant's heart-rate data and quantified the variance of the daily HR phase (the timing of the daily heart-rate peak).

Results

Three findings stood out:

• Survivors showed measurable circadian disruption. Compared with controls, trauma survivors had less stable day-to-day sleep–wake cycles, greater variability in the timing of their daily heart-rate peaks, and a higher rhythm-adjusted resting heart rate.
• Circadian instability predicted later PTSD. Within the survivor group, those with more irregular sleep rhythms and elevated heart rate three-to-six months post-event were significantly more likely to present with clinically significant PTSD at the 8–11 month follow-up.
• The effect held after controlling for early severity. Sleep instability remained a meaningful predictor of follow-up PTSD even after accounting for initial PTSD symptom severity — suggesting circadian markers carry information that goes beyond what symptom questionnaires already capture.

Strikingly, 54% of trauma survivors in this cohort still exceeded the clinical threshold for PTSD nearly a year after the attack — underscoring just how persistent post-traumatic symptoms can be following mass-casualty events.

Why it matters

The clinical bottleneck in PTSD has always been the same: most people who experience a major trauma recover, but a meaningful fraction develop chronic symptoms — and we lack scalable tools to tell them apart early. Self-report questionnaires require the person to seek care and reflect accurately on their own state, both of which are unreliable in the aftermath of severe trauma.

What this study suggests is that the wearables many people already own — fitness trackers, smartwatches, sleep monitors — may carry a passive, continuous biological signal of who is at greatest risk. Sleep–wake regularity and circadian heart-rate dynamics can be extracted from existing devices without any active input from the user. That makes them a credible candidate for early, scalable screening in the months after a traumatic event, when targeted support and intervention could make the biggest difference.

The authors frame circadian regulation itself as a potential therapeutic target: maintaining stable sleep and rhythm patterns in trauma aftermath may not just be a marker of recovery but part of the mechanism. That opens the door to interventions — light therapy, sleep stabilisation, behavioural scheduling — that could be deployed early and at scale through the same wearable platforms used for monitoring.

The bigger picture

For the broader life-sciences research community, this paper is also a reminder of how much can be learned from real-world, ecologically valid measurement. The Magal et al. study collected no lab data — every signal came from participants going about their daily lives. That methodology is increasingly central to translational psychiatry, biomechanics, and physiology research, where the gap between controlled lab paradigms and how the body actually behaves in the world has long been a limitation.

Citation: Magal N, Netzer O, Eldar E, Mandelblit N, Sagi N, Oren M, Salomon R, Admon R. Circadian instability predicts PTSD symptom severity following mass trauma. Translational Psychiatry. Preprint: 10.1101/2025.03.19.25324240