Essential Oil-enhanced digital hypnotherapy for subclinical generalized anxiety: a study protocol for a randomized controlled trial

Background Subsyndromal generalized anxiety is highly prevalent and associated with impaired well-being, elevated stress, and functional limitations, yet affected individuals often do not meet criteria for guideline-based treatment. Scalable, low-threshold digital interventions that target psychophysiological regulation may help address this gap. Guided self-hypnosis and aromatherapy using essential oils have each demonstrated anxiolytic and relaxation-promoting effects. Combining these approaches may enhance efficacy and allow for conditioning of relaxation responses via olfactory cues. Methods This study protocol describes a randomized controlled trial evaluating the efficacy and conditioning potential of a digital self-hypnosis intervention combined with essential oil inhalation in adults with subsyndromal generalized anxiety. A total of N = 630 participants will be randomized into six groups. Four groups enter the primary efficacy analysis: (1) self-hypnosis + bergamot essential oil, (2) self-hypnosis + lavender essential oil, (3) self-hypnosis without essential oil, and (4) a minimal-intervention control. The intervention is delivered online over six weeks (Phase 1), followed by a two-week conditioning phase without hypnosis (Phase 2), in which stimulus-specific effects of the essential oils are tested. The primary outcome is subjective relaxation, measured by the Multidimensional Mood Questionnaire (MDBF) at baseline, post-intervention (6 weeks), and post-conditioning (8 weeks). Secondary outcomes include anxiety symptoms, perceived stress, sleep quality, well-being, and worry. In a voluntary subsample, heart rate variability (HRV) and pulse wave variability (PWV) will be assessed as physiological correlates of relaxation. In addition, the questionnaires are expanded to include open-ended questions, enabling an exploratory assessment of participants’ experiences, attitudes, and reflections on the intervention and its potential for sustainability. This approach complements quantitative results with qualitative insights and may reveal new perspectives for future research. Discussion This study is expected to provide evidence on the efficacy of essential oil-enhanced digital hypnosis for subsyndromal anxiety and will examine whether repeated pairing of hypnosis and olfactory stimulation induces conditioned relaxation responses. If effective, this multimodal, low-intensity intervention could represent a scalable preventive approach for individuals with increased anxiety who are not receiving formal treatment and have been medically diagnosed. Clinical Trial Registration: https://www.drks.de/search/de/trial/DRKS00039047/details , Identifier DRKS00039047.