A recent study published in the International Journal of Clinical and Experimental Hypnosis reported an interesting diurnal pattern of hypnotic responsivity; specifically, the authors found higher hypnotic responsiveness in a large sample of undergraduates in the morning and early evening. However, they did not have an explanation for this pattern of findings. This pattern is consistent, however, with the theta hypothesis of hypnotic responsivity. Further examination of the associations between brain oscillations and response to hypnosis is needed to determine if specific oscillations such as theta (a) actually facilitate response to some hypnotic suggestions, (b) merely reflect hypnotic responding, or (c) reflect another factor that itself plays a causal role in response to hypnosis.
With a sample of nearly 700 undergraduate students, the authors found support for diurnal variations in hypnotic responsiveness. Administering the Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS:A) in the morning or evening resulted in higher average scores than from afternoon sessions. The authors replicated this finding using a second independent sample. In the primary study, participants indicated the time of day that they are most alert. Matching self-reported preferred time of the day with HGSHS:A administration time did not improve hypnotic responsiveness. Considering this as well as past research, the authors argue that mid-morning may be the optimal time to be hypnotized and afternoon the least favorable.