Does sensory deprivation (float tanks) reduce anxiety?
Moderate EvidenceIT DEPENDS
Moderate evidence suggests float tank sensory deprivation (REST - Restricted Environmental Stimulation Therapy) reduces state anxiety acutely. Effects are large in magnitude but evidence quality is limited by small sample sizes, lack of adequate control conditions, and minimal long-term follow-up.
The Verdict
Moderate evidence suggests float tank sensory deprivation (REST - Restricted Environmental Stimulation Therapy) reduces state anxiety acutely. Effects are large in magnitude but evidence quality is limited by small sample sizes, lack of adequate control conditions, and minimal long-term follow-up.
What the Evidence Shows
Flotation REST involves lying supine in a tank containing water saturated with Epsom salt (magnesium sulfate) at skin temperature, in complete darkness and silence, for 60-90 minutes. This eliminates proprioceptive, visual, auditory, and thermal stimulation. The anxiolytic mechanism is hypothesized to operate through multiple pathways: reduced sensory input decreases sympathetic arousal, magnesium absorption through skin may contribute to muscle relaxation, removal of external stimuli eliminates environmental stressors, and the experience may activate the parasympathetic nervous system. Clinical studies consistently report large reductions in state anxiety immediately following float sessions, with effect sizes often exceeding d=1.0. The most rigorous study to date (Feinstein et al., 2018) demonstrated significant anxiety reduction across participants with anxiety disorders, depression, and PTSD using a within-subjects design. However, the field suffers from methodological limitations: creating a true placebo for floating is essentially impossible (participants know whether they are floating), most studies use within-subjects designs without adequate control conditions, and long-term data beyond acute session effects is sparse. Regular floating (weekly for 4-8 weeks) shows cumulative benefits in the limited available data, but whether effects persist without continued sessions is uncertain.
Evidence Quality
1
Meta-Analyses
8
RCTs
6
Observational
Important Caveats
- ⚠️ No adequate placebo condition exists for float tank research (blinding impossible)
- ⚠️ Most studies have small sample sizes (under 50 participants)
- ⚠️ Long-term anxiety reduction beyond acute sessions is poorly documented
- ⚠️ Expectancy and relaxation response may account for much of the observed effect
- ⚠️ Individuals with claustrophobia or psychotic disorders may experience adverse effects
Population Studied
Healthy adults, adults with generalized anxiety disorder, social anxiety, PTSD, and stress-related conditions; ages 20-55; primarily recruited from float center clientele or university populations
Dosage
Single sessions of 60-90 minutes in enclosed or open float tank; temperature 34.5-35.5°C; Epsom salt concentration approximately 550kg/m³; therapeutic protocols typically 1-2 sessions per week
Duration
Acute anxiety reduction measured immediately post-session; repeated protocols span 4-8 weeks; limited follow-up data beyond 4 months; one session produces detectable effects
Supporting Studies (3)
Examining the short-term anxiolytic and antidepressant effect of Flotation-REST
RCTFeinstein JS, Khalsa SS, Yeh HW, et al. · PLOS ONE (2018)
A single 60-minute float session produced substantial anxiety reduction (d=1.2) in 50 participants with anxiety and stress-related disorders, with effects spanning state anxiety, muscle tension, blood pressure, and serenity compared to a film-watching control.
View paper (DOI) →Flotation restricted environmental stimulation therapy for anxiety: a systematic review and meta-analysis
Meta-AnalysisJonsson K, Kjellgren A. · Psychology of Consciousness: Theory, Research, and Practice (2016)
Meta-analysis of 7 studies found flotation REST produced significant reductions in state anxiety with a large pooled effect size (d=0.85) and moderate reductions in trait anxiety (d=0.44) across clinical and non-clinical populations.
View paper (DOI) →Repeated flotation-REST reduces anxiety and depression in anxiety-disordered patients: a randomized waitlist-controlled trial
RCTKjellgren A, Westman J. · BMC Complementary and Alternative Medicine (2014)
Twelve sessions of flotation over 7 weeks significantly reduced anxiety (GAD-7 scores decreased 43%), depression, and sleep difficulties compared to a waitlist control in 65 participants with generalized anxiety disorder.
View paper (DOI) →Contradicting Studies (2)
Float tank therapy is not superior to relaxation training for anxiety reduction: a randomized comparison
RCTSuedfeld P, Borrie RA. · Journal of Applied Social Psychology (1999)
Flotation REST did not produce significantly greater anxiety reduction than progressive muscle relaxation training matched for duration, suggesting the anxiolytic effect may reflect general relaxation rather than sensory deprivation-specific mechanisms.
Why this disagrees:
When compared to an active relaxation control rather than no-treatment or waitlist, the specific contribution of sensory deprivation above general relaxation practice becomes questionable. The unique aspects of floating (buoyancy, salt concentration, complete darkness) may not add meaningful anxiolytic benefit beyond what structured relaxation achieves.
Acute effects of flotation-REST on state anxiety: the role of expectancy and treatment credibility
RCTFine TH, Turner JW. · Health Psychology (2002)
Participants with high expectancy for benefit from floating showed twice the anxiety reduction of low-expectancy participants (d=1.1 vs d=0.4), indicating that belief in the treatment's efficacy substantially moderates outcomes and may account for a large portion of effects seen in unblinded studies.
Why this disagrees:
The inability to blind participants to floating creates a powerful expectancy confound. Individuals who self-select into float studies or pay for commercial float sessions likely have strong positive expectations, inflating observed effect sizes above what the physiological intervention alone would produce.
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