How do Sensory Deprivation tanks work?

For those of you following Stanger Things as religiously as I do, or having watched Fringe, a sensory deprivation tank or floatation tank may not be something unheard of. In fact, you may have spent several slow evenings wondering if you could replicate one in your own house to channelize your (undiscovered) telekinetic powers.  For those of you wondering what I am going on about, a sensory deprivation tank is a device or contraption filled with water which, simply put, cuts the person off from any external stimulation – be it light, sound or gravity. 

The idea of such floatation tank or Sensory Deprivation tank was first envisaged by John C. Lilly, a neuroscientist, in the year 1954. The first isolation tank was made with 160 gallons of water with salt, where everything apart from the participants’ head was submerged in water and he was made to wear a “blackout mask” which ensured no external stimulus in form of light or sound could reach him/her. However, this experiment by him took an unexpected detour when he started using LSD, a hallucinogenic drug and Ketamine, a form of anaesthetic that is known to send the consumer to a trance-like state. 

Despite this, these tanks saw commercial success in the 1970s where health centres and spas started using it for its seemingly great health benefits. 

How does it function?

Image result for sensory deprivation tanks diagram

Floatation tanks are can easily be found at several floatation centres across the globe. They have been largely recognised to effectively help with problems like stress, pain and more. The concept is essentially used to perform restricted environmental stimulation therapy (REST) – a technique for sensory deprivation having known physical and mental benefits to the user.

As for the commercial tanks that are used today, they are filled with about a foot of water which is saturated with 800 pounds of Epsom salt to make the body float. The Tank is made of material which makes it completely soundproof and the lid is such that no light can also enter into the tank. 

So basically, a user is completely devoid of any external stimulus and in such a state the body starts relaxing and even though the person does not sleep, he enters a trance-like stage with very shallow breathing. 

Effects of Floatation Tank 

The idea behind making such a device was actually to study the origin of human consciousness. However, it is now a recognised method of REST and has several recognised physiological and psychological benefits. Some of the major benefits include:

  • A heightened sense of introspection and out-of-body experiences: Akin to the benefits of extensive meditation or sound sleeping state, this practice has been reported to be linked to “decreased alpha waves and increased theta waves in the brain”. Something similar to the Overview Effect astronauts experience.
  • Improving athletic capabilities: In a study conducted in 2016 on 60 elite, international-level athletes (28 male, 32 female) across a range of 9 sport, for effect of Floatation on body soreness and other related issues, it was found that this method seemed to work on both physical and mental issues faced by an athlete post-training.  
  • Muscle relaxation: The addition of Epsom salts to the water, in addition to increasing the buoyancy, also is deemed to be an effective muscle relaxant.
  • Other benefits: In a meta-analysis published in 2007 on 27 independent studies also outlined several physiological benefits such as low blood pressure, lower anxiety levels etc. In fact, the study also suggested it to be an effective stress management tool. 

Apart from these, it has also been related to improved focus, increased creativity, lesser burnouts and other mental imbalances. However, its use hasn’t completely been controversy-free. Several detrimental impacts have also been recorded while using this technique. The negative impacts include hallucinations and out-of-body experiences by certain people. A study conducted in 2009 showed that in case of both hallucination prone and non-hallucination prone individuals, when exposed to sensory deprivation, there were clear signs of perceptual disturbances, paranoia, and anhedonia. In several cases where the person suffered from claustrophobia, it is said to cause difficulty in breathing among other things. 
In conclusion, despite clear medical benefits being associated with this practice, a trip to your doctor is advisable before booking your own session in the nearest floatation centre, to correctly foresee the effects it may have on your body and mind. 


Christina Daniel and Oliver J. Mason “Predicting Psychotic-Like Experiences during Sensory Deprivation” available at (2015).