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Evidence Library · Mindfulness & Sensory Therapies

Mindfulness & Sensory Therapies · AXIOM SELENE

Float Tanks (Sensory Deprivation / REST) — What the Evidence Actually Shows

A 2025 systematic review of 63 studies found consistent signals for stress and anxiety reduction — but the most rigorous chronic pain trial found no long-term benefit over placebo, sleep evidence is limited, and most anxiety research comes from a single research group. Here is what the science shows, and what it does not yet confirm.

Evidence grade

Preliminary evidence — Single study or observational data — association, not proven causation

5 sources9 documented gapsLast verified: 2026-06-28

What Float Tanks Are

Flotation-Restricted Environmental Stimulation Therapy (flotation-REST) involves floating supine in a shallow pool of body-temperature water saturated with Epsom salt (magnesium sulphate), inside an enclosed chamber that blocks light and sound entirely. The high salt concentration makes the body effortlessly buoyant without effort. Sessions typically run 60–90 minutes. By removing input from visual, auditory, thermal, tactile, vestibular, gravitational, and proprioceptive channels simultaneously, the therapy creates an unusually low-demand state for the nervous system. First developed in the 1950s by neurophysiologist John Lilly and later systematised as 'REST,' float tanks have moved from niche research into mainstream wellness retreats globally, including across Southeast Asia.

Anxiety and Stress: The Strongest Signal in the Research

The most consistent finding across flotation-REST studies is a reduction in state anxiety and subjective stress. A 2018 PLoS One study by Justin Feinstein and colleagues at the Laureate Institute for Brain Research measured state anxiety, mood, and physical symptoms in 50 people with clinical anxiety disorders before and after a single 60-minute float — reporting a large within-person effect. A 2024 single-blind randomised controlled trial (n=75) confirmed that six sessions were feasible and safe in anxious and depressed adults. The 2025 BMC systematic review found stress reduction was statistically significant across all six studies that examined it. However, the strong anxiety signals come primarily from one research group, and no large-scale efficacy RCT for anxiety has yet been completed.

~ Probable (incomplete evidence)
A single 60-minute float session produced a large reduction in state anxiety (Cohen's d = 2.15) in 50 people with clinical anxiety disorders, with concurrent decreases in muscle tension, pain, and depressive symptoms.

🅰 PLoS One — Short-term anxiolytic and antidepressant effect of Floatation-REST (n=50 clinical, 2018)— Single-arm pre-post design — no blinded active control. Cohen's d = 2.15 is a within-person effect that cannot exclude expectation, relaxation response, or time effects. Independent replication with a controlled design is needed before this is considered established.

✓ Proven
Six sessions of floatation-REST are safe, feasible, and well-tolerated in individuals with clinical anxiety and depression, with no serious adverse events.

🅰 PLOS One — Randomized controlled safety and feasibility trial of floatation-REST in anxious and depressed individuals (n=75, 2024)— This specific claim — safety and feasibility — is confirmed by the RCT design and is the trial's stated primary outcome. The trial was not powered to confirm efficacy; it supports the safety case for a larger efficacy trial, which has not yet been completed.

~ Probable (incomplete evidence)
Stress reduction was statistically significant across all six studies on stress examined in the 2025 systematic review of flotation-REST.

🅰 BMC Complementary Medicine and Therapies — Systematic Review of Flotation-REST 2025 (63 studies, 1,838 participants)— Narrative finding from a systematic review of heterogeneous studies. 'Significant' reflects individual study p-values, not a pooled meta-analytic effect size. Most individual studies are small.

Chronic Pain: Promising in Small Studies, No Long-Term Benefit in the Largest RCT

The 2025 BMC systematic review found '100% significant results' for pain management across nine quantitative studies. However, the largest and most rigorously controlled trial — a single-blind, placebo-controlled RCT of 99 chronic pain patients published in JAMA Network Open in 2021 — produced a different picture. Both the flotation-REST group and the placebo group improved in the short term on pain intensity, relaxation, and anxiety, but there were no significant differences between groups at 1, 12, or 24 weeks. The small-study optimism and the controlled-trial null result sit in direct tension, and the discrepancy is not yet explained.

~ Probable (incomplete evidence)
Float REST produces short-term improvements in pain intensity and relaxation — but so did the placebo control, and no between-group advantage was found at 1, 12, or 24 weeks in the only adequately controlled trial.

🅰 JAMA Network Open — Flotation REST for Chronic Pain: randomized controlled trial (n=99, 2021)— Loose et al. 2021 (n=99). Short-term improvement is 'probable' given both groups improved; this cannot be attributed specifically to floating based on this trial. The null long-term finding (no advantage over placebo) is the primary evidence-level conclusion for chronic pain.

✗ No evidence found
Float REST delivers reliable or lasting pain relief after a course of sessions.

🅰 JAMA Network Open — Flotation REST for Chronic Pain: randomized controlled trial (n=99, 2021)— Not confirmed by the only adequately controlled RCT, which found no long-term benefit over placebo. Positive findings in smaller studies may reflect placebo effects or small-study bias.

Sleep: Limited and Mixed Evidence

Sleep is one of the most commonly marketed benefits of float tanks. The 2025 BMC systematic review found 'limited to no effect' for sleep-related conditions — one of only two outcome domains where flotation-REST did not show consistent positive results. An earlier pilot study of six people with diagnosed insomnia found mixed results: three improved on their primary sleep complaint, three did not, and the two who benefited most were young adults with sleep-onset insomnia specifically. The evidence base for sleep is too small and inconsistent to support a confident recommendation.

✗ No evidence found
Float REST reliably improves sleep quality or is an effective treatment for insomnia.

🅰 BMC Complementary Medicine and Therapies — Systematic Review of Flotation-REST 2025 (63 studies, 1,838 participants)— The 2025 systematic review specifically categorised sleep as showing 'limited to no effect' across examined studies. The only dedicated insomnia study (n=6) had mixed results and is far too small to draw conclusions.

The Brain: Early fMRI Evidence — Interesting but Unreplicated

A 2021 Human Brain Mapping study conducted the first functional MRI scan study of flotation-REST. Forty-eight healthy adults were randomised to 90 minutes of floating or 90 minutes of seated rest, then scanned. Those who floated showed decreased resting-state functional connectivity between the default mode network (DMN) and the somatomotor cortex — brain regions involved in self-referential thinking and bodily self-monitoring. Floaters also reported greater increases in serenity and decreases in anxiety than the chair-rest group. The authors provide an initial neurological mechanism for the mental effects of floating, but explicitly flag the need for replication.

~ Probable (incomplete evidence)
A 90-minute float session reduces resting-state functional connectivity between the default mode network and somatomotor cortex, compared to seated rest in a controlled design.

🅰 Human Brain Mapping — fMRI study of Floatation-REST and default mode network connectivity (n=48, 2021)— Al Zoubi et al. 2021. First and only fMRI study on flotation-REST. Authors identify replication as a necessary next step, and note that the 8-minute resting scans used may have limited test-retest reliability. Small neuroimaging sample (24 per group).

What the Research Does Not Yet Tell Us

Several common marketing claims about float tanks are not yet supported by the evidence. Float REST has not been shown to boost the immune system in any reviewed study. Detoxification claims have no controlled evidence base. The strong anxiety signals are promising but come predominantly from a single research group; independent replication in a blinded efficacy trial has not yet been completed. Long-term benefits beyond a short course of sessions are essentially unstudied. Optimal protocol — session length, frequency, water temperature, number of sessions — is not established, since studies used widely varying approaches. The therapy appears well-tolerated and low-risk for most healthy adults, but specific populations (cardiovascular conditions, severe claustrophobia, pregnancy) are not represented in the research.

What we don't yet know

Honesty about gaps in the evidence is what distinguishes us from most wellness media.

  • Independent replication: most anxiety and stress research (including the most-cited single-session study) originates from one research group — the Laureate Institute for Brain Research (Feinstein et al.). Findings need confirmation from independent teams before they are considered established.
  • No large-scale efficacy RCT for anxiety or depression exists. The 2024 RCT (n=75) confirmed safety and feasibility only — it was not powered to confirm that flotation-REST reduces anxiety more than a control condition.
  • Chronic pain: the largest controlled trial (JAMA 2021, n=99, placebo-controlled) found no long-term benefit over placebo. The gap between the consistent small-study signal and the null RCT result is not explained by current evidence.
  • Sleep: the systematic review found 'limited to no effect,' directly contradicting a common marketing claim. The only dedicated insomnia pilot study had six participants.
  • Long-term effects: virtually no studies follow participants beyond 12–24 weeks. Whether benefits persist or compound with regular long-term use is unknown.
  • Optimal protocol is not established. Studies vary widely in session length (45–90 minutes), number of sessions (1–12), frequency, and tank design — limiting comparisons and clinical guidance.
  • The fMRI brain connectivity finding (2021) is from a single study of 48 people and has not been replicated. The neural mechanism for anxiety reduction remains speculative.
  • Specific-population safety: no controlled studies exist for people with cardiovascular conditions, claustrophobia, open skin wounds, or pregnancy. Recommendations for these groups cannot be made from published research.
  • Comparison across tank formats (enclosed tank vs. open float pool) has not been studied — it is unknown whether the enclosure itself contributes to effects.

All sources

This article describes what published research has found about flotation-REST. It is not medical advice. Float tanks are not a substitute for evidence-based treatment of clinical anxiety, depression, chronic pain, or insomnia. Consult a healthcare professional before using flotation therapy if you have any health conditions, including cardiovascular disease, claustrophobia, skin conditions, or pregnancy.

Last verified: 2026-06-28 · ← Evidence Library