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Reactivating a Relaxation Exercise During Sleep to Influence Cortical Hyperarousal in Individuals With Frequent Nightmares

Clara Sayk, Alicia Probst, F. Lange, Svenja Eickemeier, J. Amores, Hong‐Viet V. Ngo, M. Ehsanifard, Klaus Junghanns, Ines Wilhelm

Journal of Sleep Research September 9, 2026 DOI: 10.1111/jsr.70443 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Randomized, blinded, crossover laboratory study Peer reviewed
Sample size 25
Population Adults experiencing at least one nightmare per week (21 female, mean age 23.12 years, SD 3.70)
Duration 1-week deep breathing relaxation training; two laboratory nights
Measures Beta (16.25-31 Hz) power, gamma (31.25-45 Hz) power, spindle count, spindle density, subjective wake-after-sleep-onset, nightmare symptoms
Topics Dreaming
Key points Odour-cued reactivation of a practiced deep-breathing relaxation exercise did not influence beta or gamma power or nightmare symptoms, but was unexpectedly associated with a significantly reduced spindle count and density. Spindle count during reactivation nights correlated positively with subjective wake-after-sleep-onset. The authors conclude that the intervention did not modulate cortical hyperarousal or nightmares, and that the functional significance of the spindle effect remains to be determined.

Abstract

High-frequency EEG activity during sleep, reflecting cortical hyperarousal, has recently been incorporated into aetiology models of nightmares. However, its precise role remains insufficiently understood because experimental approaches to manipulate hyperarousal during sleep are limited. In the present study, we investigated whether re-presenting a relaxation-associated odour cue during sleep to reactivate a previously practiced deep-breathing relaxation exercise reduces cortical hyperarousal as indexed by beta (16.25-31 Hz) and gamma (31.25-45 Hz) activity and, consequently, nightmare symptoms. Twenty-five participants (21 female, mean age (SD) = 23.12 (3.70) years) experiencing at least one nightmare per week completed a 1-week deep breathing relaxation training paired with an odour cue. In a randomised, blinded, crossover design, either the relaxation-associated odour or a control odour was presented across two laboratory nights. Odour-based reactivation did not influence beta or gamma power but was unexpectedly associated with a significantly reduced spindle count and density. Spindle count during reactivation nights correlated positively with subjective wake-after-sleep-onset. Nightmare symptoms were unaffected. These findings suggest that odour-cued reactivation of a relaxation exercise did not modulate cortical hyperarousal or nightmare symptoms, despite altering spindle activity. The functional significance of this spindle effect remains to be determined. Future studies should employ longer reactivation periods and alternative interventions targeting cortical hyperarousal to further clarify its causal role in nightmare aetiology and the therapeutic potential of sleep-based interventions.

In the evidence

This study is part of the evidence base for a synthesis in the library. Here is how each one recorded it.

  • State of the evidence: Dreaming No effect

    Odour-cued reactivation of a relaxation exercise did not influence beta or gamma power or nightmare symptoms, but was unexpectedly associated with reduced spindle count and density; spindle count correlated positively with subjective wake-after-sleep-onset.

    Synthesized

Comparable studies

Other randomized controlled trials on dreaming, most cited first.

Study Year Design Participants
Efficacy of a Cognitive‐Behavioral Treatment for Insomnia and Nightmares in Afghanistan and Iraq Veterans With PTSD Combat veterans of Operation Enduring Freedom and/or Operation Iraqi Freedom (mean age... 2013 Randomized controlled trial n = 40
Lucid Dreaming Treatment for Nightmares: A Pilot Study Chronic nightmare sufferers 2006 Randomized controlled trial n = 23
Testing the involvement of the prefrontal cortex in lucid dreaming: A tDCS study Participants spending three consecutive nights in a sleep laboratory 2013 Randomized controlled trial n = 19
Pre-sleep treatment with galantamine stimulates lucid dreaming: A double-blind, placebo-controlled, crossover study Adults with high dream recall and an interest in lucid dreaming 2018 Randomized crossover trial n = 121
Studies with lucid dreaming as add-on therapy to Gestalt therapy Adults with nightmares (ICD-10: F51.5) at least twice a week 2015 Randomized controlled trial n = 32

Citations in the library

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