Hypnotizability, sleepiness, and subjective experience.

The relationships between hypnotizability, sleepiness, and the subjective experience of hypnotic suggestions were investigated in 90 participants. Scores from the Harvard Group Scale of Hypnotic Susceptibility Form A (HGSHS:A), the Karolinska Sleepiness Scale (KSS), the Epworth Sleepiness Scale (ESS), the Pittsburgh Sleep Quality Index (PSQI), and our self-developed Questionnaire on Subjective Hypnotic Experiences (QSHE) were analyzed. Findings show that hypnotizability correlates with both habitual daytime sleepiness and instantaneous sleepiness after the hypnotic procedure. Results also indicate that subjective self-evaluation of responses to hypnotic suggestions may be a useful tool in some cases when comparing with other subjectively rated scales, such as those concerning sleepiness.