Float Therapy

Sensory deprivation research in the 1950s and 1960s

A 2025 systematic review states that it appears the physician John C. Lilly built the first sensory deprivation tank in 1954 while working at the US National Institute of Mental Health. That first prototype had users suspended upright under water, wearing breathing masks, with a safety operator monitoring them. The review adds that Lilly seems not to have published specific scientific papers on the topic in those decades, so the account of his role rests on secondary description.

The same review separates this water-immersion work from the dry or chamber form of restricted environmental stimulation that Donald Hebb studied, in which people lay on a bed in a soundproof, lightproof room for sessions of up to 24 hours. It also reports that in 1960 Jay Shirley sought to standardize flotation procedures by controlling light, sound, vibration, odor and temperature.

The horizontal salt-water tank and later research

According to the review, Lilly later worked with the engineer Glenn Perry on a design in which a person lies horizontally in a solution highly saturated with Epsom salt (magnesium sulfate). Commercial versions released in the 1970s were built shallower and added water filtration, which made upkeep easier. Modern tanks are described as more often rounded or oval than the early rectangular form.

The review credits Peter Suedfeld with beginning flotation research in 1968 and with coining the term Restricted Environmental Stimulation Therapy, and notes a large share of later academic work from Anette Kjellgren and colleagues at Karlstad University in Sweden from the 2000s. It also mentions functional magnetic resonance imaging studies by Justin Feinstein's group in the United States. These dates come from one review and were not checked against the original publications.

REST and flotation-REST

Restricted environmental stimulation therapy (REST) is the research term for techniques that place a person in an environment with minimal sensory input. Flotation-REST is the form that uses an enclosed tank of salt water, and the same review lists float pod, float tank and sensory deprivation tank as other names for the equipment. Chamber-REST, in which a person lies on a bed in a dark, quiet room, is a different procedure and is excluded from the flotation literature.

Wellness and clinical usage

Public-facing labels such as float therapy, flotation therapy and float pod are used for the same tank-based experience. A chronic pain trial used the clinical name flotation restricted environmental stimulation therapy and compared it with a placebo condition run in the same tank. The scoping review of flotation-REST for chronic pain describes tanks as dark, soundproof environments resembling large bathtubs with lids. The word therapy in these names describes how the practice is offered and studied, and does not by itself indicate a recognized treatment for any condition.

The tank and the water

In the studies reviewed, a person lies on their back in a tank of shallow water saturated with Epsom salt, which makes the body float without effort. The water is held near skin temperature, about 35 degrees Celsius (95 degrees Fahrenheit) in the Swedish trials. One Swedish pilot trial reported a tank holding 600 liters of water and 350 kilograms of magnesium sulfate. The enclosure is dark and soundproof. In the German pain trial, the water was kept at about 35 degrees Celsius, and participants were told the low water level was for safety.

Session length and schedule

The scoping review found that flotation sessions in pain studies ranged from 45 to 90 minutes, most commonly 45 minutes. The German pain trial used five sessions of 60 to 90 minutes, four days apart, and let participants contact staff by intercom after 60 minutes to end or extend a session. The two Swedish randomized pilots used twelve 45-minute sessions over seven weeks. These are research schedules, and commercial float centers may offer different formats.

Who attends

A 2026 cross-sectional survey of 61 users recruited from an online forum and a float center in the southwestern United States found that over half were long-term and monthly users. Compared with national survey benchmarks, they more often reported depression, daily anxiety and sleep disturbance, and more often reported moderate-intensity exercise and muscle soreness. The authors state the design cannot show that flotation changed any of these measures.

Uses proposed in the research literature

The 2025 systematic review sorted 63 studies of flotation-REST into applications including pain, athletic performance, physiology, stress, consciousness, psychology, creativity, clinical anxiety, sleep and smoking cessation. Individual trials have examined stress-related muscle tension pain, generalized anxiety, recovery from exercise, and insomnia.

Practitioners and the authors of these studies describe flotation as a route to deep relaxation. That description is a proposed explanation, and the sources reviewed do not establish the mechanism. The sources reviewed also do not document the commercial claims made by float centers, so this page does not evaluate them.

Users and the reasons they float

The 2026 survey of float users found that, compared with a national benchmark, respondents more often reported depression, daily anxiety and sleep disturbance, which is consistent with people using flotation in connection with such concerns. The survey did not ask users to rank their reasons, and its authors note it cannot show whether flotation changed these measures.

Systematic and scoping reviews

A 2025 systematic review searched to May 2024 and found 63 studies with 1,838 participants. Its authors report positive effects on pain, athletic performance, stress, mental well-being and clinical anxiety, and limited to no effect on sleep-related disorders and smoking cessation. They caution that the number of studies in some categories is small, that publication bias cannot be ruled out, and that mechanisms and optimal protocols are unclear.

A 2026 scoping review limited to chronic pain, searched to January 2025, included eight studies with 401 participants, six of them randomized trials. It reports consistent improvements in pain intensity and frequency in most studies and variable effects on sleep and physiological outcomes. Heterogeneity in protocols, outcome measures and follow-up prevented meta-analysis, and the authors call for high-quality randomized trials.

Placebo-controlled trial in chronic pain

A single-blind randomized trial at Hannover Medical School assigned 99 adults with chronic pain disorder to five flotation sessions, a placebo condition in the same tank without effortless floating or stimulus restriction, or a wait list. There were no differences between groups on the primary outcome, the change in pain intensity one week after the last session, or on long-term secondary outcomes at 12 and 24 weeks. Short-term improvements in pain, relaxation and anxiety appeared in the flotation group, and similar changes in the placebo group. The authors conclude that the improvements may not be caused by stimulus restriction or effortless floating.

Wait-list trials in anxiety and in healthy adults

A non-blinded randomized pilot in 50 adults with self-reported generalized anxiety disorder compared twelve sessions with a wait list. Anxiety symptoms fell in the flotation group and not in the wait-list group, and the authors report that most improvements were maintained at six months. Diagnosis rested on self-report measures and there was no active comparator. A randomized pilot in 65 healthy employees with the same schedule reported lower stress, depression, anxiety and worst pain, and better sleep quality and optimism, than a wait list.

A single-case study of six people with insomnia found mixed results, with no change in total sleep time, and a randomized crossover study in 24 untrained men found lower blood lactate and perceived pain after a one-hour float but no difference in muscle strength or soreness. Wait-list designs cannot separate the effect of flotation from expectation or from time spent resting.

Reported harms and how they were recorded

The scoping review states that no adverse events were reported in any of its included pain studies, and the generalized anxiety pilot reports that no negative effects were found. Absence of reported harm in small trials is limited reassurance, because the sources reviewed do not describe systematic adverse-event monitoring, and none of them is a safety study. This page found no case series or pharmacovigilance summary on float tanks.

Exclusion criteria used in trials

Trials excluded people for reasons that indicate where caution has been applied. The German pain trial excluded pregnancy, acute illness, contagious disease, acute major depression, epilepsy, claustrophobia, schizophrenia and incontinence. The Swedish anxiety pilot excluded pregnancy, a pacemaker, open wounds or skin disease, epilepsy, a history of psychosis, bipolar syndrome, post-traumatic stress disorder and ongoing substance misuse. These lists reflect study design, are not clinical guidance, and the sources reviewed do not say that each exclusion was based on observed harm.

Gaps in the sources and care boundaries

The sources reviewed do not cover tank hygiene, water quality, drowning or fainting risk, or any training standard or professional register for float operators, and no such body was found. Float therapy does not replace assessment or treatment for pain, anxiety, sleep disorders or other conditions, and a person with a medical condition on the exclusion lists above can ask a clinician whether a session is appropriate.