Cardiovascular psychophysiology of stress-inducing and relaxing imagery following a hypnotic induction.

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Though hypnotic imagery is frequently used in clinical practice to help manage stress-related symptoms and disorders, the psychophysiology and autonomic effects are still debated. Parasympathetic and sympathetic autonomic nervous system (ANS) branches can be differentially quantified to assess how physiology is altered, but previous research has found contradictory evidence regarding specific effects of hypnosis. It is also unknown whether cognitive and somatic processes are differentially influenced by hypnotic imagery. Understanding how hypnotic imagery impacts individuals (psychologically and physiologically) is imperative for clinicians developing interventions and could provide evidence for which symptoms might best respond. This dissertation aimed to determine the effects of hypnotic imagery on self-report stress, relaxation, and autonomic physiology, and to assess whether self-report changes were associated with physiological changes. Hypnotizability was explored as a potential moderator. Sixty participants listened to a voiced recording with stress-inducing, neutral, and relaxing imagery, which followed a hypnotic induction or sham hypnosis (white noise), depending on randomization. Parasympathetic (HF HRV) and sympathetic (PEP) cardiovascular effects were assessed continuously, and self-report stress and relaxation were measured with numeric rating scales at five timepoints: baseline, neutral, stressful, and relaxing imagery, and endpoint. Physiological and self-report measures changed significantly across the five timepoints, but physiological effects were not significantly different between hypnosis and white noise groups, suggesting that the imagery conditions created autonomic changes regardless of whether a hypnotic induction preceded. Interestingly, physiological effects and corresponding self-report ratings were not strongly correlated. PEP and stress ratings were significantly correlated during the relaxing hypnotic imagery only, and HF HRV and relaxation ratings were not correlated during any timepoints. Lastly, hypnotizability moderated the effect of imagery conditions on self-report ratings but not on physiological measures. A notable limitation of the study is that a large proportion of participants scored low in hypnotizability, potentially skewing results toward weaker effects, as low hypnotizable individuals would be expected to have less pronounced physiological changes during hypnosis. The current findings point to the crucial need for further research into the roles of hypnosis inductions and of hypnotic imagery.

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Psychophysiology. Hypnosis. Imagery. Autonomic. Hypnotic induction.

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