Sensory Deprivation (Flotation) Tanks: Here’s What You’re Missing

Flotation tanks (or “sensory deprivation tanks”) are an underestimated weapon in a world of external stimuli. Here’s an overview of the benefits of flotation tanks, backed by scientific research.

Give this question some consideration. When was the last time you were awake but without external stimuli?

Lying in bed in darkness before you go to sleep? Unlikely. Chances are you can still hear the vague outline of the outside world, see the faint outlines of objects and furniture around you.

While meditating in a quiet room? Maybe. But with kids running around or the buzz of a smartphone notification, distraction is never far away. Even a potential distraction can be a distraction.

Truth be told, when I ask myself this question, it’s hard to think of any state without external stimuli. That is, perhaps, until I return to before I was even born.

Yes, for most of us, our time in the womb is our moment of peak sensory deprivation. From birth onwards, life becomes a sensory firework display. We are bombarded with sights, tastes, scents, sounds and textures no sooner than we have made our arrival.

Technologies play their role in upgrading this firework display, too. We hospitably accept a constant stream of unique sights and sounds through screens. Our neurochemistry embraces the dopamine by design.

Wouldn’t it be nice, then, to occasionally shut ourselves off from all the external stimuli?

Well, perhaps we can. Enter the flotation tank.

What Is a Flotation Tank?

A flotation tank is a large tank filled with water which contains enough Epsom salt to allow you to float without effort. Inside, the tanks are lightproof and soundproof, with water maintained at skin temperature. Sessions in a flotation tank typically last one or two hours.

The central idea of flotation tanks is simple: to provide an environment shut off to external stimuli, eliminating as many of the senses as possible. As a result of this key characteristic, flotation tanks are often referred to as “sensory deprivation tanks”. The scientific research, however, tends to refer to avoid this term due to its negative connotations, using the term “Flotation-REST” (which stands for Reduced Environmental Stimulation Therapy).

Flotation tanks are associated with a wide range of benefits (more on the scientific research shortly) but have primarily gained in popularity through high-profile use. John Lennon is said to have conquered his heroin addiction through floating. Richard Feynman, the Nobel Prize-winning physicist, described the mind-expanding effects of flotation in his autobiography. Joe Rogan has mentioned his home flotation tank on numerous occasions on his podcast, claiming it offers a unique form of meditation and an area for exploring ideas.

So, to whom do they owe a debt of gratitude?

Who Invented the Flotation Tank?

The flotation tank was invented by a scientist called John C. Lilly in 1954. Lilly was a brilliant and unconventional scientist who was fascinated by human consciousness. He is perhaps best known for his multi-decade interest in human communication with dolphins and for the self-administration and study of psychedelics.

Lilly put forward a variety of theories as a result of ketamine-induced visions. These include the existence of a hierarchical group of cosmic entities and the idea of “Solid State Intelligence”, where he predicted that human-made computers would eventually develop into an autonomous “bioform”.

(When I said unconventional, I meant it. I recommend diving down the rabbit hole and exploring some of Lilly’s wide-ranging research. He was an extraordinary man and led an extraordinary life.)

Benefits of Flotation Tanks

At an anecdotal level, it’s easy to see how Lilly’s invention supports relaxation and meditation. But how do these benefits extend into the cold rigor of science? And are there other benefits to using flotation tanks that sit beneath the surface of individual testimonies and anecdote?

After reading about John Lilly and some of the testimonies of flotation tank users, I wanted to find out more. There seemed to be far more to flotation tanks than met the eye. And so I did what geeks do best: I dived into the research.

#1: Stress management

The single most common reported benefit of flotation tanks across all the journal articles that I read is relaxation – and consequently, stress management. Flotation tanks provide a space to ground one’s thoughts but above all, to relax without external stimuli. It’s perhaps unsurprising that this reflects in the data.

A study in 2014 from the Human Performance Laboratory at Karlstad University in Sweden found that after 12 flotation sessions over a period of 7 weeks, self-reported stress was significantly decreased. Participants also reported benefits such as improved sleep, reduced anxiety and reduced pain.

A small 2010 study also found that flotation tanks might be a useful intervention for those suffering from “burn out”, particularly when used in conjunction with psychotherapy.

This effect seems to play out at the physiological level. Numerous studies report that float users experience lower blood pressure and lower cortisol levels. In 2004, two researchers from the Netherlands conducted a meta-analysis of 27 different studies covering 449 participants. Despite some limitations with early studies, their results overwhelmingly show that flotation tanks have positive physiological effects, lowering blood pressure and levels of cortisol.

Both of these measures are closely tied to the body’s stress response, reinforcing the idea that flotation tanks can be an effective stress management tool.

#2: Improved sleep

Perhaps as a direct consequence of improved stress management, flotation tank users consistently report improved quality of sleep. A 2020 meta-analysis of 9 studies found that in all studies reviewed “flotation-REST demonstrated beneficial effects on sleep”. In fact, in two of those studies, the benefits for sleep endured for up to half a year post-treatment.

Even those undertaking a single float session might experience some benefit for sleep. A small thesis study found that insomniacs reported significantly improved sleep quality 2 weeks after a single flotation session. Further peer-reviewed research is needed to validate this one-time impact.

#3: Reduced anxiety

The benefits of flotation tanks appear to extend beyond day-to-day stress management and may well offer an effective alternative or supplementary treatment for anxiety disorders.

In research published in 2018, 50 participants were recruited across a spectrum of anxiety and stress-related disorders (including PTSD, generalized anxiety and panic disorder). The researchers measured self-reported anxiety before and after a one-hour float session and found that anxiety levels were significantly reduced. The most severely anxious participants reported the largest effects.

A follow-on study from the same group of researchers looked at the impact of float sessions on interoceptive awareness – which basically means the awareness of sensations within one’s own body. The study found that a 90-minute float session significantly increased awareness and attention for cardiorespiratory sensations. It might be argued that forming a new connection between relaxation and bodily sensations can be particularly beneficial for those who have drawn a rigid link between bodily sensations and their anxiety.

Similarly, a 2016 study of generalized anxiety disorder (GAD) also showed promising results. Researchers found that a 12-session programme of floating was associated with significant reductions in symptoms. These results potentially offer a unique alternative treatment for GAD, which remains one of the least successfully treated forms of anxiety. The researchers note, however, that we need more research at larger scale to confirm these findings.

#4: Reduced mind wandering

Flotation tank users often describe the experience as a form of enhanced meditation. Joe Rogan calls it his “extreme meditation”. Tim Ferriss calls it “meditation on steroids”.

The neurochemistry in action provides some revealing confirmation of this perspective. A recent study found that the activity in the default-mode network (DMN) – that’s the mind wandering region of our brain – appears to be lower in flotation tank users. Lower DMN activity supports the idea that regular flotation tank use might enable us to become more present and spend less time worrying about the past or future. It also echoes the type of neurological impact we see from meditation.

#5: Improved creativity

Here’s where the benefits start to move beyond mental health. Following on from Lilly’s ventures into consciousness and creativity with psychedelics in flotation tanks, academics have sought to separate the noise of psychedelics from the noise of flotation tanks. Numerous controlled studies have looked at the creative performance of flotation tank users versus control groups – and with noteworthy results.

Take, for example, this study from 1992. Researchers tested participants’ creativity before and after flotation sessions using the Guilford Fluency Test. Float participants showed significant increases in their test scores after flotation, as well as improved performance on other thinking measures. The improvement was significantly higher than the control group.

Key Concept: The Guilford Fluency Test. Researchers often use this test to assess divergent thinking and creativity. The methodology is simple but incredibly effective. An everyday object is first presented to a participant, such as coffee mug, a pen or a fork. The participant then has to come up with as many uses for that object as possible, no matter how silly they might seem. For testing fluency, we simply count the number of ideas. The Guilford test is also often expanded to assess flexibility, originality and elaboration.

#6: Imagery and improved performance

The role of flotation tanks for imagination might also offer benefits that extend beyond innovation and creativity. A number of elite performers use flotation tanks as an environment in which they can visualize and perfect their craft. This imagery process seems to be enhanced in environments where external stimuli are limited.

Indeed, there are a variety of studies which appear to demonstrate the effects of imagery and pre-performance flotation relative to regular relaxation techniques. I found research supporting this idea for basketball players, tennis players, archers and rifle marksmanship. In all cases, elite performers that used flotation tanks for imagery saw a large relative improvement in subsequent performance.

It’s fair to assume that we can extrapolate some of these effects across other disciplines. Indeed, there is plenty of anecdotal evidence. NFL players, for example, have been using flotation tanks to gain an edge.

#7: Improved recovery and pain management

The performance benefits also seem to extend to physical recovery and pain management. For example, a 2013 study found that flotation-REST had a significant impact on blood lactate and perceived pain when used after leg exercises.

Another study looked at the effects of flotation tanks for those suffering with chronic muscle aches and pains. The results indicated that severe perceived pain intensity was significantly reduced, but lower levels of pain were not.

Epsom salts: One hypothesis for the improvement in recovery and pain is the role of Epsom salts, which breakdown into magnesium and sulfate in water. Epsom salt baths have been used for centuries as home treatments for psoriasis, arthritis pain, fatigue, insomnia and muscle aches.

#8: Altered states of consciousness

Perhaps one of the most understated benefits of flotation tanks is uncoincidentally one of the most controversial. That is, the role of altered states of consciousness. Many advocates of flotation tanks see them as the closest thing to a psychedelic experience without using actual psychedelics. Flotation tanks are said to induce “mystical experiences” in some and a degree of ego dissolution.

Qualitative analyses report altered states of consciousness ranging from milder states, such as altered time perception and feelings of weightlessness, to more powerful perceptual changes, such as out-of-body experiences.

Flotation tanks appear to have promise for inducing altered states of consciousness, but there is a need for further research to understand this role.

Disadvantages of Flotation Tanks

So, is it all upside? And if so, why aren’t these things everywhere?

Problem #1: Cost and size

The first problem is cost and size. Quality flotation tanks are too expensive and too big for most of us to have in our homes. I looked at the time of writing and a decent flotation tank would comfortably set you back over $20,000 – and that’s before we consider maintenance and running costs.

Most people therefore tend to go to flotation centres for a one-hour or two-hour floating session. Such sessions typically cost upwards of $75 per session.

In short, it may be a good habit but it’s not a cheap one.

Problem #2: Hallucinations (although rare)

The benefits we’ve talked about here aren’t universal for everyone. In fact, for those that have a particular vulnerability to hallucination, flotation tanks might do more harm than good. A 2015 study grouped participants according to hallucination proneness and found that the high proneness group reported more psychotic-like experiences (PLEs).

It’s worth noting here that this sounds worse than it is. Reports of hallucinations are quite rare and don’t endure once outside the tank. Nonetheless, for those with predispositions for hallucinations, this is a trade-off that warrants consideration before jumping into a flotation tank.

Problem #3: The role of sensitivity

It also seems that the more sensitive the person, the more profound the flotation experience. One study found that a group with highly sensitive persons (there is a special scale for this in psychology research) “experienced significantly more mystical experiences and higher degree of altered states of consciousness during the treatment” when compared to a less sensitive group.

Of course, that’s not to say lower-sensitivity people will get no benefits, just that they might be less pronounced.

Problem #4: Overstated benefits

There are a lot of documented benefits, but perhaps the most important caveat here is to take these findings with a pinch of salt. Flotation tank providers have latched onto many of these findings and often overstate the benefits.

Bottom line: flotation tanks are probably a useful tool, but aren’t going to turn you into superman. In addition, we need further research to fully understand and confirm some of the findings.

Summary

We’ve covered a lot of ground, so let’s sum up:

  • Flotation tanks (also known as sensory deprivation tanks) are lightproof and soundproof tanks filled with enough skin-temperature Epsom salt water to allow you to float without effort.
  • Flotation tank sessions have been linked with a number of mental and physiological benefits, which include improved stress management, improved sleep, reduced anxiety, lower blood pressure, improved performance and creativity, and altered states of consciousness.
  • Further research is needed to fully understand the benefits of flotation tanks and confirm some of these findings.

While we’ve reviewed a lot of promising research – some recent and some longstanding – one reality is unlikely to change in future: the experience varies from person to person.

If we want to find out more, eventually we must take the plunge into the darkness and Epsom salt for ourselves.

If you do decide to start flotation, or if you have a prior experience you would like to share, feel free to get in touch here. I’m keen to hear perspectives that don’t end up in academic journals and news articles. And as I continue my own journey in the world of flotation, I will of course add my thoughts onto this article.

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