Please select the eligibility criteria that correspond to the clinical trial below.
Title: A Phase I, Multi-centre, Double-blind, Placebo-controlled Parallel Group Study to Assess the pharmacoMRI Effects of AZD6765 in Male and Female Subjects Fulfilling the Criteria for Major Depressive Disorder
Brief Summary: The purpose of this study is to determine the effect of a single dose infusion of AZD 6765 compared with placebo and ketamine on the blood oxygen level dependent signal using fMRI (functional Magnetic Resonance Imaging) in depressed subjects.


Options:
A: Inclusion Criteria:

* Documented clinical diagnosis meeting criteria from the DSM-IV by structured clinical interview,major depressive disorder, single episode or recurrent
* Outpatient status at screening and at randomisation

Exclusion Criteria:

* A major depression disorder which has a major impact on the subjects current psychiatric status
* Subjects not allowed to use mood stabilizers, antidepressants or other antipsychotic or psychoactive drugs
* Subjects with lifetime history of schizophrenia, bi-polar, psychosis and psychotic depression
B: Inclusion Criteria:

* At the time of signing the informed consent form (ICF), participant must be a man or woman 18 (or older if the minimum legal age of consent in the country in which the study is taking place is greater than \[\>\]18) to 64 years of age, inclusive
* At the start of the screening/prospective observational phase, participant must meet the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) diagnostic criteria for single-episode major depressive disorder (MDD) (if single-episode MDD, the duration must be greater than or equal to \[\>=\] 2 years) or recurrent MDD, without psychotic features, based upon clinical assessment and confirmed by the Mini-International Neuropsychiatric Interview (MINI)
* At the start of the screening/prospective observational phase, participant must have an Inventory of Depressive Symptomatology-Clinician rated ( IDS-C30) total score of greater than or equal to (\>=) 34
* At the start of the screening/prospective observational phase, participants must have had non-response (less than or equal to \[\<=25\] percent \[%\] improvement) to \>=1 but less than or equal to (\<=) 5 (if current episode is \>2 years, upper limit is applicable to only the last 2 years) oral antidepressant treatments taken at adequate dosage and for adequate duration, as assessed using the Massachusetts General Hospital - Antidepressant Treatment Response Questionnaire (MGH-ATRQ) and documented by medical history and pharmacy/prescription records, for the current episode of depression.

Participant is taking a different oral antidepressant treatment on the MGH-ATRQ for at least the previous 2 weeks at or above the minimum therapeutic dose

- The participant's current major depressive episode, depression symptom severity (Week 1 MADRS total score \>=28 required), and antidepressant treatment response in the current depressive episode, must be confirmed using a Site Independent Qualification Assessment

Exclusion Criteria:

* Participants who have previously demonstrated nonresponse of depressive symptoms to esketamine or ketamine in the current major depressive episode, to all 4 of the oral antidepressant treatment options available for the double-blind induction phase (i.e, duloxetine, escitalopram, sertraline, and venlafaxine extended release \[XR\]) in the current major depressive episode (based on MGH-ATRQ), or an adequate course of treatment with electroconvulsive therapy (ECT) in the current major depressive episode, defined as at least 7 treatments with unilateral/bilateral ECT
* Participant has received vagal nerve stimulation (VNS) or has received deep brain stimulation (DBS) in the current episode of depression
* Participant has a current or prior DSM-5 diagnosis of a psychotic disorder or MDD with psychotic features bipolar or related disorders (confirmed by the MINI), obsessive compulsive disorder (current only), intellectual disability (DSM-5 diagnostic codes 317, 318.0, 318.1, 318.2, 315.8, and 319), autism spectrum disorder, borderline personality disorder, antisocial personality disorder, histrionic personality disorder, or narcissistic personality disorder
* Participant has homicidal ideation/intent, per the investigator's clinical judgment, or has suicidal ideation with some intent to act within 6 months prior to the start of the screening/prospective observational phase, per the investigator's clinical judgment or based on the Columbia Suicide Severity Rating Scale (C-SSRS)
* Participants with history of moderate or severe substance or alcohol use disorder according to DSM-5 criteria
C: Key Inclusion Criteria:

* Age 18 - 65
* Currently meets DSM-5 criteria for MDD
* Body Mass Index between 18 and 40 kg/m\^2, inclusive

Key Exclusion Criteria:

* Suicide risk
* History of treatment resistance in current depressive episode
* History of electroconvulsive therapy, vagus nerve stimulation, transcranial magnetic stimulation or any experimental central nervous system treatment during the current episode or in the past 6 months
* Pregnant, breastfeeding, or planning to become pregnant or breastfeed during the study
D: Inclusion Criteria:

* between the ages of 18 and 65 years old
* diagnosed with depression and being referred for ECT
* American Society of Anesthesiologists (ASA) score of 1 or 2
* patient receiving ECT on an informal basis (i.e. consenting to treatment and able to give informed consent)

Exclusion Criteria:

* pre-existing neurological disease or cognitive impairment
* co-morbid psychiatric diagnoses
* pre-existing hypertension
* severe respiratory tract disease
* major cardiovascular disease
* pacemakers
* cerebrovascular disorder or malformation
* intracranial mass lesions
* seizure disorder
* intracranial electrode or clips
* intra-ocular pathology
* endocrine or metabolic disease
* severe hematologic disease
* severe fracture
* not able to give consent
* pregnancy

Answer: A