Can a single infusion or a crisis plan stop suicide? new trial aims to find out

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: Participants must meet all of the following criteria: 1. Age 14 years or older. 2. Presentation to a participating public emergency service (ED/UEU) in Indaiatuba, São Paulo, Brazil. 3. Either of the following: 1. A suicide attempt within the previous 30 days, including an actual, interrupted, or aborted attempt; OR 2. Current severe suicidal ideation, defined as endorsement of item 4 or 5 of the Columbia-Suicide Severity Rating Scale (C-SSRS) screening version: active suicidal ideation with intent to act, without a specific plan (item 4), or with a specific plan (item 5). Non-suicidal self-injury alone does not satisfy this criterion. 4. Residence within the study catchment area in Indaiatuba, enabling completion of follow-up assessments. 5. Ability to provide written informed consent for participants aged 18 years or older, or written assent with written informed consent from a parent or legal guardian for participants aged 14-17 years. 6. No clinical decision for voluntary or involuntary admission to a psychiatric inpatient unit following the index emergency evaluation. Exclusion Criteria: Participants meeting any of the following criteria are excluded: 1. A contraindication to esketamine, including aneurysmal vascular disease, arteriovenous malformation, a history of intracerebral hemorrhage, or known hypersensitivity to esketamine or ketamine. 2. Current pregnancy or breastfeeding. Pregnancy testing is performed in the emergency setting for participants with pregnancy potential; breastfeeding status is established by clinical history. 3. Medical instability requiring intensive care unit admission without feasible study follow-up. 4. A primary psychotic disorder, such as schizophrenia or schizoaffective disorder; or current acute psychosis or an acute manic episode that precludes informed participation. 5. Any of the following substance-related conditions: 1. Acute intoxication at assessment that precludes valid informed consent, reliable administration of the C-SSRS, or safe delivery of the assigned intervention, as determined by the attending physician. Re-screening is permitted after clinical recovery if all other eligibility criteria remain satisfied. For participants qualifying on the basis of a recent suicide attempt, that attempt must still fall within the preceding 30 days. 2. High-risk hallucinogen involvement, defined as a WHO ASSIST substance-specific involvement score of 27 or higher for the hallucinogen category, item (h). 3. A documented history of ketamine use disorder identified during baseline psychiatric assessment. 6. Inability to maintain contact for follow-up assessments. Substance-use assessment: The Brazilian Portuguese WHO ASSIST is administered during baseline eligibility assessment. Substance-specific involvement scores are calculated from questions 2 through 7, with question 5 omitted for tobacco. Questions 1 and 8 do not contribute to these scores. High risk is defined as a score of 27 or higher. The ASSIST hallucinogen category does not identify ketamine exposure specifically; relevant substance history is also assessed clinically. Except for the high-risk hallucinogen criterion above, ASSIST scores do not automatically exclude participation. Among eligible participants, high-risk involvement with alcohol or other non-tobacco substances is recorded for exploratory moderation analyses and to inform clinical care.