This early-stage trial aims to examine the feasibility, tolerability, and safety of Floatation-REST (Reduced Environmental Stimulation Therapy) or an active comparison condition in 50 individuals receiving treatment for Amphetamine-Type Substance Use Disorder.

Methamphetamine Use Disorder (MUD) is associated with a barrage of mental and physical health problems including heightened drug craving/relapse/overdose rates, comorbid mood and anxiety disorders, and cardiovascular dysfunction. Unfortunately, MUD is becoming more prevalent. In the U.S., methamphetamine-related treatment admissions are increasing, as are methamphetamine-related deaths in recent years. Despite this substantial burden, there are currently no FDA approved pharmacological treatments for methamphetamine use disorder.

Recent models of addiction highlight the potential role that negative reinforcement plays in relapse, such that stress and negative affect increase drug craving, thereby increasing the likelihood of future drug seeking behaviors despite negative consequences. Consistent with this model, individuals may persist in methamphetamine use to avoid aversive states such as anxiety, depression, fatigue, and other withdrawal symptoms, a cycle known as negative reinforcement. Floatation-REST (Reduced Environmental Stimulation Therapy is a novel non-pharmacologic intervention that has been shown to reduce anxiety/stress in anxious and depressed individuals. It seems plausible that it may have the potential to lessen these aversive states in methamphetamine users, which may also relate to decreased state drug craving/urges to use. To our knowledge, no studies have tested the feasibility/tolerability and safety of floatation-REST in individuals with methamphetamine-type substance use disorder.

The current study investigates the safety and feasibility/tolerability of a single session of floatation-REST in treatment-seeking individuals with methamphetamine use disorder, relative to an active comparator. In this within-subject crossover design, participants will complete two counterbalanced sessions: one in a floatation pool (Pool-REST), and the other in a floatation chair (Chair-REST). Safety and tolerability will be assessed by self-report questionnaires as well as via pre- and post-session ratings of anxiety, stress, and drug craving. Feasibility will be assessed by intervention adherence rate. Findings from this study will inform the design of future feasibility and efficacy studies as well as mechanistic studies of recovery from methamphetamine addiction.

Inclusion Criteria:

• Between 18-55 years of age
• Meeting criteria for a primary DSM-5 diagnosis of current methamphetamine use disorder
• Has completed at least two weeks of inpatient treatment (translating into having at least two weeks of drug/alcohol sobriety) at one of the two recruitment sites (Grand Addiction and Recovery Center or Women In Recovery) and is still currently enrolled in this treatment at the time of the study
• Capable of completing all measures during each session of the experiment: able to provide written informed consent and must have sufficient proficiency in the English language to understand and complete interviews, questionnaires, and all other study procedures.

Exclusion Criteria:

• Has any of the following DSM-5 disorders: Schizophrenia Spectrum and Other Psychotic Disorders OR Bipolar I Disorder
• Participant fails to adhere to our "Pre-float checklist".
• Any antihistamine that causes drowsiness (e.g., Benadryl).
• Caffeine or nicotine consumed within the past 2 hours.
• Reports a history of unstable liver or renal insufficiency; glaucoma; diabetes; significant and unstable cardiac, vascular, pulmonary, gastrointestinal, endocrine, neurologic, hematologic, rheumatologic, or metabolic disturbance; or any other condition that, in the opinion of the investigator, would make participation not be in the best interest (e.g., compromise the well-being) of the subject or that could prevent, limit, or confound the protocol-specified assessments.
• A breathalyzer test positive for alcohol or a drug-positive urine test at either session.
• Non-correctable vision or hearing problems.
• Unwillingness or inability to complete major aspects of the study protocol (e.g., floating). However, failing to complete some individual aspects will be acceptable (e.g., being unwilling to answer individual items on a questionnaire).

The investigator and participant are masked to study arm until after the participant completes their baseline assessment visit, at which point they are randomized using a sealed envelope.