Importance: Limitations of current antidepressants highlight the need to identify novel treatments for major depressive disorder. A prior open trial found that a single session of whole-body hyperthermia (WBH) reduced depressive symptoms; however, the lack of a placebo control raises the possibility that the observed antidepressant effects resulted not from hyperthermia per se, but from nonspecific aspects of the intervention.
Objective: To test whether WBH has specific antidepressant effects when compared with a sham condition and to evaluate the persistence of the antidepressant effects of a single treatment.
Design, setting, and participants: A 6-week, randomized, double-blind study conducted between February 2013 and May 2015 at a university-based medical center comparing WBH with a sham condition. All research staff conducting screening and outcome procedures were blinded to randomization status. Of 338 individuals screened, 34 were randomized, 30 received a study intervention, and 29 provided at least 1 postintervention assessment and were included in a modified intent-to-treat efficacy analysis. Participants were medically healthy, aged 18 to 65 years, met criteria for major depressive disorder, were free of psychotropic medication use, and had a baseline 17-item Hamilton Depression Rating Scale score of 16 or greater.
Interventions: A single session of active WBH vs a sham condition matched for length of WBH that mimicked all aspects of WBH except intense heat.
Main outcomes and measures: Between-group differences in postintervention Hamilton Depression Rating Scale scores.
Results: The mean (SD) age was 36.7 (15.2) years in the WBH group and 41.47 (12.54) years in the sham group. Immediately following the intervention, 10 participants (71.4%) randomized to sham treatment believed they had received WBH compared with 15 (93.8%) randomized to WBH. When compared with the sham group, the active WBH group showed significantly reduced Hamilton Depression Rating Scale scores across the 6-week postintervention study period (WBH vs sham; week 1: -6.53, 95% CI, -9.90 to -3.16, P < .001; week 2: -6.35, 95% CI, -9.95 to -2.74, P = .001; week 4: -4.50, 95% CI, -8.17 to -0.84, P = .02; and week 6: -4.27, 95% CI, -7.94 to -0.61, P = .02). These outcomes remained significant after evaluating potential moderating effects of between-group differences in baseline expectancy scores. Adverse events in both groups were generally mild.
Conclusions and relevance: Whole-body hyperthermia holds promise as a safe, rapid-acting, antidepressant modality with a prolonged therapeutic benefit.
Trial registration: clinicaltrials.gov Identifier: NCT01625546.