The study proposed in this protocol aims to document the physiological, subjective, behavioral, and neural effects of reduced environmental stimulation (floating) in patients with current or prior anorexia nervosa The primary aim of this study is to determine the safety of this intervention. Secondary aims including determining whether floating has an impact on symptom reports such as those related to anxiety and eating disorders.

Floating creates an environment with minimal visual, auditory, tactile, proprioceptive, and thermal input to the brain. The float rooms used in this study are both lightproof, and thus completely dark when the entry door is sealed and the lights are turned off, reducing all visual input to the brain. Each float room was constructed with thick soundproof walls, restricting most outside noises from entering the room, thereby reducing auditory input to the brain. A high concentration Epsom salt water solution allows individuals to effortlessly float on their back while remaining completely still, reducing both proprioceptive and tactile input to the brain. The temperature of the water is calibrated to the temperature of the skin (~94° F) and the temperature of the air is calibrated to the temperature of the water, making it difficult to discern the boundary between air and water, thus reducing thermal input to the brain while minimizing the need for thermoregulation of the skin.

While both float pools dramatically reduce external sensory information, it is important to note that participants are in full control over the experience. For example, participants can enter and exit the float pool whenever they choose. Each float pool also contains a blue LED light that can be turned on and off via an air-coupled light switch in the pool. Both float rooms contain a shower for cleaning before and after floating.

In a prior study the investigators have found that healthy participants found the pool condition to be relaxing and stress relieving. The current study aims to determine the safety of floating with a clinical population, specifically individuals with a history of eating disorder who are of normal weight.

Inclusion Criteria:

1. Current or prior diagnosis of anorexia nervosa (AN)
2. All AN participants must be weight-restored prior to their participation, defined as having a Body Mass Index (BMI) > 17.5

Exclusion Criteria:

1. Any of the following DSM-V disorders:

   1. Schizophrenia Spectrum and Other Psychotic Disorders
   2. Bipolar and Related Disorders

2. Currently being treated for their psychiatric condition as an inpatient.

3. Active suicidal ideation with intent or plan (as determined by a psychiatrist or clinical psychologist for all participants who report an IDAS-II suicide score > 10).

4. Morbid obesity (BMI > 40) or underweight (BMI < 17.5).

5. Orthostatic hypotension (defined as a drop of ≥20 mm Hg in systolic blood pressure or a drop of ≥10 mm Hg in diastolic blood pressure when measured shortly after transitioning from lying down to standing).

6. Certain drugs or medications consumed within the past week including any psychoactive drugs (e.g., MDMA, LSD, psilocybin, peyote, phencyclidine, ketamine), magnesium supplements (greater than 150mg) or milk of magnesia. Any antihistamine that causes drowsiness (e.g., Benadryl) or any alcohol consumed within the past 12 hours. Caffeine or nicotine consumed within the past 3 hours. For all other medications, participants must be stably medicated prior to participation (defined as having taken the medication for 6 weeks or longer).

7. History of unstable liver or renal insufficiency; glaucoma; diabetes; significant and unstable cardiac, vascular, pulmonary, gastrointestinal, endocrine, neurologic, hematologic, rheumatologic, or metabolic disturbance.

8. Pregnancy as detected by a urine test.

9. Failure to adhere to "Pre-float checklist".

10. Non-correctable vision or hearing problems.