Effects and Feasibility of Hyperthermic Baths for Patients with Depressive Disorder: A Randomized Controlled Clinical Pilot Trial

Background Evaluation of efficacy, safety and feasibility of hyperthermic baths (HTB; head-out-of-water-immersion in 40°C), twice a week, compared to a physical exercise program (PEP; moderate intensity aerobic exercises) in moderate to severe depression.

Method Single-site, open-label randomized controlled 8-week parallel-group pilot study at an university outpatient clinic as part of usual depression care. Medically stable outpatients with depressive disorder (ICD-10: F32/F33) as determined by the 17-item Hamilton Depression Rating Scale (HAM-D) score ≥18 and a score ≥2 on item 1 (Depressed Mood) were randomly assigned to receive either two sessions of HTB or PEP per week (40-45 min) provided by two trained doctoral students. An independent biometric center used computer-generated tables to allocate treatments. Primary outcome measure was the change in HAM-D total score from baseline (T0) to the 2-week time point (T1). Linear regression analyses, adjusted for baseline values, were performed to estimate intervention effects on an intention-to-treat (ITT) principle.

Findings 45 patients (HTB n = 22; PEP n = 23) were randomized and analyzed according to ITT (mean age = 48.4 years, SD = 11.3, mean HAM-D score = 21.7, SD = 3.2). Baseline-adjusted mean difference was 4.3 points in the HAM-D score in favor of HTB (p<0.001). This improvement was achieved after two weeks. Compliance with the intervention and follow-up was far better in the HTB group (2 vs 13 dropouts). There were no treatment-related serious adverse events. Main limitation: the number of dropouts in the PEP group (13 of 23) was far higher than in other trials investigating exercise in depression (18.1 % dropouts).

Conclusions HTB seems to be a fast-acting, safe and easy accessible method leading to clinically relevant improvement in depressive disorder after two weeks; it is also suitable for persons who have problems performing exercise training.

Trial registration German Clinical Trials Register (DRKS) with the registration number DRKS00011013 (registration date 2016-09-19) before onset of the study.