The Science Of Sensory Deprivation And Why It Calms The Body
What decades of research show about cortisol, blood pressure, and the nervous system's response to floating.
Float therapy has moved from a 1950s research curiosity into mainstream wellness studios, and the newest trials are measuring its effect on stress hormones directly.
Takeaways
Removing sensory input lowers cortisol
Effects show up within a single session
Blood pressure drops during the float itself
Anxiety relief can last past 48 hours
Repeated sessions may compound the benefit
This is the second piece in a series looking at modern recovery and wellness treatments.
The Old Standard: Talk Therapy And Medication Versus Removing Input Altogether
Most stress treatment works by adding something. Talk therapy adds a structured conversation. Medication adds a chemical intervention. Float therapy, formerly called flotation Restricted Environmental Stimulation Therapy, or REST, works by taking something away.
A person lies in 10 to 12 inches of water saturated with roughly 1,000 pounds of Epsom salt, warmed to skin temperature, in a chamber with no light and no sound. The body floats without effort. There's nothing to see, hear, or feel pressing against the skin.
The idea dates back further than most people assume.
Psychiatrists Jay Shurley and John Lilly began testing sensory deprivation at the National Institute of Mental Health in the 1950s to understand how the brain behaves with no external input. Early versions required a breathing helmet and full submersion.
Modern float pods are far less clinical, but the underlying question researchers are still asking hasn't changed: what does the body do when it stops receiving nearly all outside sensory signals at once?
Old standard: Manage stress through medication, conversation, or physical exertion, all of which add stimulation of some kind.
New approach: Remove visual, auditory, tactile, and gravitational input simultaneously, and let the nervous system respond to the absence.
Old standard: Measure success mostly through self-reported mood.
New approach: Track cortisol, blood pressure, and heart rate directly during and after sessions.
The Science: What Happens When The Brain Loses Its Sensory Input
Cortisol is the body's primary stress hormone, released by the adrenal glands to help manage the fight-or-flight response. Under chronic stress, cortisol stays elevated longer than it should, which is linked to poor sleep, high blood pressure, and weakened immune response over time. Flotation REST appears to interrupt that pattern directly rather than just making someone feel calmer.
A meta-analysis pooling 27 studies and 449 participants found that flotation REST produced a strong overall effect on physiological stress markers, including reduced cortisol and lower blood pressure, with an overall pre-to-post effect size of 1.02, a large effect by most research standards (van Dierendonck & Te Nijenhuis, 2005).
One of the earlier controlled studies in that body of work tracked plasma cortisol across eight sessions and found both the average level and the session-to-session variability dropped significantly in the float group, with no change in a seated-rest control group (Turner & Fine, 1991, as cited in the 2023 systematic review).
More recent clinical work has pushed further into anxiety and depression specifically. A 2018 open-label study of 50 participants with anxiety and stress-related disorders found a single one-hour float session produced a large reduction in state anxiety, with an effect size researchers described as unusually strong for a single session of any intervention (Feinstein et al., 2018).
A companion study using a crossover design recorded blood pressure drops averaging more than 12 mmHg during the float itself, alongside increased awareness of internal bodily sensations like heartbeat and breath (Feinstein et al., 2018).
An Expert's Perspective: Promise And Prudence
The research base has grown enough that a 2023 systematic review was able to pull together 60 studies covering 1,838 participants across pain, athletic performance, stress, anxiety, sleep, and smoking cessation. Here's what holds up across that wider body of evidence:
Cortisol and blood pressure respond quickly. Physiological stress markers move within a single session, not just after repeated use, which separates float therapy from interventions that need weeks to show measurable change.
Anxiety relief can outlast the session. Multiple trials report anxiolytic effects persisting for 48 hours or longer after a single float, though the effect fades without repeated sessions.
Repeated use compounds the benefit. A 2024 randomized feasibility trial testing eight weeks of biweekly floats found sustained improvements that single-session studies can't capture on their own.
Not every claimed benefit holds equally well. The 2023 systematic review found limited to no effect on sleep disorders and smoking cessation, areas where float therapy is sometimes marketed more aggressively than the data supports.
Float pods are not a treatment for diagnosed psychiatric conditions on their own, and researchers running these trials are careful to frame float therapy as a complement to existing care, not a replacement for medication or therapy in people with clinical anxiety or depression. People with certain skin conditions, open wounds, or claustrophobia are also generally advised against floating, or should start with an open-pod option rather than an enclosed tank.
Benefits At A Glance
Category | Benefit |
Stress Hormone Reduction | Removing sensory input lowers cortisol output, with measurable drops within a single session. |
Cardiovascular Response | Blood pressure drops noticeably during floating, with recorded average reductions of more than 12 mmHg. |
Anxiety Relief | A single float session can meaningfully reduce state anxiety, with effects reported to last 48 hours or longer. |
Muscle Relaxation | Zero-effort buoyancy in magnesium-rich Epsom salt water eases muscle tension without requiring any physical exertion. |
Interoceptive Awareness | Removing outside stimuli sharpens attention to internal signals like heartbeat and breath. |
Nervous System Recovery | Reduced sympathetic arousal supports a shift toward calmer, parasympathetic nervous system activity. |
Sleep-Related Effects | Evidence here is weaker; systematic reviews report limited to no consistent effect on sleep disorders. |
The Road Ahead
Float therapy sits in an interesting spot. The physiological evidence for cortisol and blood pressure changes is fairly consistent across five decades of research, which is longer than most wellness trends can claim. Dosing's still being worked out. How many sessions, spaced how far apart, produce the most durable effect. Current trials are testing weekly and biweekly schedules over six to eight weeks, but there's no settled clinical protocol yet the way there is for, say, a course of physical therapy.
Expect more research pairing float therapy with existing anxiety and depression treatment rather than testing it alone, more attention to which formats work best for people who find full enclosure uncomfortable, and continued caution about the claims that outrun the data, particularly around sleep and addiction. The mechanism is simple to describe. Take away the input, and the nervous system can stop responding to it.
What's likely next: more trials pairing float therapy with existing anxiety and depression treatment rather than testing it alone, wider adoption in clinical and rehab settings beyond wellness studios, and clearer guidance on who should avoid it, including people with certain skin conditions, open wounds, or severe claustrophobia. For now, the practice works best framed the way the research frames it. Not a miracle. A tool, with real mechanisms behind it, that rewards getting the details right. |
FAQs
How long does it take to feel the effects of a float session?
Most studies measure changes within the first 30 to 45 minutes of a 60-minute session, with cortisol and blood pressure shifts appearing before the session ends.
Is float therapy safe for people with high blood pressure?
Floating tends to lower blood pressure acutely, which is generally considered safe, but anyone on blood pressure medication should check with a doctor before starting.
Do you need multiple sessions to see a benefit, or does one float work?
A single session produces measurable effects on cortisol and anxiety, but researchers running repeated-session trials found the benefits build and last longer with consistent use.
What's the difference between an open float pod and an enclosed tank?
Both use the same water and salt setup, but open pods leave more visual space around the body, which tends to suit people who feel uneasy in fully enclosed spaces.
Can float therapy replace anxiety medication?
No. Every clinical trial testing float therapy for anxiety has framed it as a complementary tool alongside existing treatment, not a replacement for medication or therapy.
Coming up in the series: cryotherapy and how it differs from a cold plunge, infrared sauna on its own, compression therapy for circulation, LED light therapy for skin and tissue repair, and NAD+ IV treatments, examined with the same mix of research and caution.
Note: Background on recovery-modality offerings referenced for context: Pause Studio — float service descriptions used to ground the practical framing of this article.
Sources
Van Dierendonck, D., & Te Nijenhuis, J. (2005). Flotation restricted environmental stimulation therapy (REST) as a stress-management tool: A meta-analysis. Psychology & Health, 20(3), 405–412. https://www.tandfonline.com/doi/full/10.1080/08870440412331337093
Feinstein, J. S., Khalsa, S. S., Yeh, H., Al Zoubi, O., Arevian, A. C., Wohlrab, C., Pantino, M. K., Cartmell, L. J., Simmons, W. K., Stein, M. B., & Paulus, M. P. (2018). Examining the short-term anxiolytic and antidepressant effect of Floatation-REST. PLOS ONE, 13(2), e0190292. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5796691/
Feinstein, J. S., Khalsa, S. S., Yeh, H., Wohlrab, C., Simmons, W. K., Stein, M. B., & Paulus, M. P. (2018). The elicitation of relaxation and interoceptive awareness using floatation therapy in individuals with high anxiety sensitivity. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, 3(6), 555–562. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6040829/
A systematic review of Flotation-Restricted Environmental Stimulation Therapy (REST). (2023). medRxiv. https://www.medrxiv.org/content/10.1101/2023.11.29.23299203v1.full
Jonsson, K., Grim, K., & Kjellgren, A. (2024). A randomized controlled safety and feasibility trial of floatation-REST in anxious and depressed individuals. Journal of Affective Disorders Reports. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11156321/
Source Note
This piece draws on recovery-modality framing from Pause Studio. All physiological and clinical claims are sourced directly from the peer-reviewed studies and systematic reviews cited above, prioritizing the most recent available trial data.
Important Health Notice: This article provides general healthcare information and should not replace professional medical guidance. For specific health concerns, always consult your healthcare provider first.
