The impact of floatation therapy on body image and anxiety in anorexia nervosa: a randomised clinical efficacy trial

BACKGROUND: Body image disturbance and anxiety are core features of anorexia nervosa (AN), a psychiatric disorder with one of the highest mortality rates. This study examined the efficacy of a novel non-pharmacological treatment, floatation-REST (Reduced Environmental Stimulation Therapy) on body image disturbance and anxiety in inpatients with AN. METHODS: This parallel group randomised controlled trial compared floatation-REST vs. care as usual in women and girls hospitalised for treatment of AN in Tulsa, Oklahoma, USA. Participants were randomised on a 2:1 ratio to receive eight, twice-weekly, 60-min floatation-REST sessions for 4 weeks, in addition to care as usual, or to receive care as usual. The primary outcome was the average change in body dissatisfaction from pre- to post-float as measured by the Photographic Figure Rating Scale. The secondary outcome was the average change in anxiety from pre- to post-float as measured by the state version of the State Trait Anxiety Inventory. Longitudinal effects of floatation-REST on body dissatisfaction were also examined. All analyses were conducted using the intention-to-treat principle. Planned linear mixed models tested the effect of floatation-REST vs. care as usual. The trial was preregistered (clinicaltrials.govNCT03610451). FINDINGS: Between March 16, 2018 and February 25, 2021, 133 participants were screened for eligibility, and 86 were consented. Eighteen were excluded after consent, for a final randomisation sample of 68 participants (45 floatation-REST; 23 care as usual). There were two session by condition interactions on body dissatisfaction (p = 0.00026) and state anxiety (p < 0.0001), such that the floatation-REST group exhibited acute (i.e., pre- to post-session) reductions in body dissatisfaction (floatation-REST group mean change (Δm) = −0.43; 95% CI −0.56 to −0.30, p < 0.0001, Cohen’s d = 0.23), and acute reductions in anxiety (floatation-REST group Δm = −15.75; 95% CI −17.95 to −13.56, p < 0.0001, Cohen’s d = 1.52); however, the care as usual group exhibited no significant changes. With regard to longitudinal results, there was a significant time by treatment interaction between baseline and immediately post intervention (p = 0.012) and baseline and six-month follow up (p = 0.0019). At immediately post intervention, there was a trending reduction in body dissatisfaction for the floatation-REST group (Δm = −0.41, 95% CI −0.86 to 0.03, p = 0.068) and care as usual group (Δm = 0.61; 95% CI −0.04 to 1.27, p = 0.070). At six-months post-intervention, the floatation-REST group exhibited lower body dissatisfaction (Δm = −0.91; 95% CI −1.37 to −0.45, p = 0.0020, Cohen’s d = 0.53) whereas the care as usual group reported no change in body dissatisfaction (Δm = 0.35; 95% CI −0.28 to 0.98, p = 0.96) relative to baseline. There were no adverse events related to the trial during the study. INTERPRETATION: Our findings suggest that Floatation-REST decreased body dissatisfaction compared to care as usual acutely after each float session and at six-month follow-up. Floatation-REST has potential utility for the treatment of body image disturbance and anxiety in AN. These results may be limited by some generalisability concerns given the recruitment of a modest sample receiving inpatient treatment at a single site. FUNDING: 10.13039/100001380The William K. Warren Foundation.