Hypnotic suggestibility as a moderator of treatment response in mild to moderate depression: an exploratory secondary analysis

Background Hypnotic suggestibility may moderate treatment outcomes, but evidence in depression is limited and inconsistent. Objective This analysis examined whether baseline hypnotic suggestibility moderated changes in depressive symptoms over time and whether this effect differed between groups. Methods This exploratory secondary analysis used data from the HypnoDeep trial, a randomized, controlled, pilot trial. Patients with mild to moderate depressive symptoms were randomized to group hypnosis, progressive muscle relaxation (PMR), or control. Hypnotic suggestibility was assessed with the Harvard Group Scale of Hypnotic Susceptibility, Form 5 (HGSHS-5:G) and the Creative Imagination Scale (CIS) at baseline. Depressive symptoms were measured at baseline and at 6 weeks using the Beck Depression Inventory–II. Linear mixed-effects models examined whether baseline suggestibility moderated depressive symptom changes and whether this association differed between groups, adjusting for age and sex. Separate models were estimated for HGSHS-5:G and CIS. A post hoc power analysis contextualized detectable effect sizes. Results Ninety-four participants were included (mean age 39.2 years, SD 12.0; women: n = 67 [71.3%], men: n = 25 [26.6%], diverse: n = 2 [2.1%]). Baseline hypnotic suggestibility assessed with the HGSHS-5:G ranged from 0 to 5 (mean 2.9, SD 1.6), and CIS scores ranged from 2 to 35 (mean 17.6, SD 7.7). Baseline hypnotic suggestibility was not associated with differential change in depressive symptoms over time in the control group for either the HGSHS-5:G or the CIS, and there was no indication that this association differed in the hypnosis or PMR group compared with the control group (HGSHS-5:G: hypnosis β = 2.05, 95% CI −2.21 to 6.31, p = 0.350; PMR β = −0.97, 95% CI −5.14 to 3.20, p = 0.651; CIS: hypnosis β = 3.06, 95% CI −1.36 to 7.48, p = 0.179; PMR β = −0.44, 95% CI −4.49 to 3.61, p = 0.833). Post hoc power analysis indicated that complete-case group sizes were insufficient to reliably detect small-to-moderate associations. Conclusion Exploratory analyses did not indicate that hypnotic suggestibility moderated changes in depressive symptoms across groups. Given limited statistical power, findings are preliminary and hypothesis-generating. Larger studies are needed to clarify treatment-response moderators.