Repetitive Transcranial Magnetic Stimulation for People With Etomidate Addiction (SToP-E-rTMS x Etomidate)

The goal of this clinical trial is to learn if high-frequency rTMS works to treat etomidate addiction in adults. It will also learn about the safety and tolerability of rTMS. The main questions it aims to answer are: * Does active rTMS reduce craving, amount of etomidate use, frequency of etomidate use, and severity of etomidate use disorder? * Does active rTMS improve cognitive biases related to delayed reward discounting and risk sensitivity? * What side-effects do participants have when receiving rTMS? Researchers will compare active rTMS to sham rTMS to see if active rTMS works to treat etomidate addiction. Participants will: * Receive active rTMS or sham rTMS over 4 weeks * Complete 20 rTMS sessions in total * Visit the clinic for treatment sessions and follow-up assessments * Complete assessments of etomidate use, craving, withdrawal symptoms, mood symptoms, cognition, and decision-making Attend follow-up assessments up to 6 months after baseline

Inclusion Criteria: * Able to read and communicate in English and/or Chinese * Able to give informed consent and/or able to provide an informed consent from the legal guardian (if applicable) * Using etomidate and/or its related analogues as the primary psychoactive substance of abuse * Suffering from etomidate addiction as defined by: 1. Etomidate Use Disorder classified under "Sedative-, Hypnotic-, or Anxiolytic Use Disorder" according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR) with severity ≥ 1, or 2. Harmful Use or Dependence for etomidate classified under "Mental and behavioral disorders due to use of sedatives or hypnotics" according to the International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10), or 3. Hazardous use, harmful use or dependence classified under "Hazardous use of sedatives, hypnotics or anxiolytics" or "Disorders due to use of sedatives, hypnotics or anxiolytics" according to the Clinical descriptions and diagnostic requirements for International Classification of Diseases 11th Revision (ICD-11) mental, behavioral, and neurodevelopmental disorders. Exclusion Criteria: * Age \< 18 years old * Unable to read English or Chinese * Unable to give informed consent * Had been diagnosed with the following disorders including: 1\. Neurodevelopmental Disorders: * DSM-5: Intellectual Disabilities, Communication Disorders, Specific Learning Disorder, Autism Spectrum Disorder and Motor Disorders * International Statistical Classification of Diseases and Related Health Problems 11th Revision (ICD-11): Disorders of intellectual development (6A00), Developmental speech or language disorders (6A01), Autism spectrum disorder (6A02), Developmental learning disorder (6A03), Developmental motor coordination disorder (6A04), Stereotyped movement disorder (6A06), Primary tics or tic disorders (8A05.0) * Other DSM-5 defined Substance Use Disorder greater than moderate in severity (i.e., severity score ≥4) * Neurocognitive Disorders (DSM-5, or ICD-11 6D70-72 \& 6D80-86) 2. Contra-indicated to undergo rTMS: * with electronic and/or magnetic implants (e.g., pacemaker, implantable cardioverter defibrillator \[ICD\], cerebral shunts, cochlear implant, etc.) * with metallic or mechanic fragments (e.g., screws, plates, stents, clips, etc.) * pregnant * with any known or history of neurological conditions including cerebral vascular accidents (CVA), epilepsy, brain tumor or space occupying lesion, etc. * poorly controlled or unstable diabetes mellitus * receiving unstable dose(s) of antipsychotics, antidepressants, benzodiazepines and/or anticonvulsants in the past 3 months