# Recreational Nitrous Oxide Use and Associated Neuropsychiatric Presentations in Patients Attending the Emergency Department

## TL;DR

This study examines the neuropsychiatric effects of recreational nitrous oxide use in emergency department patients, finding associations with psychosis, self-harm, and neurological symptoms.

## Contribution

The study provides new clinical insights into the neuropsychiatric presentations linked to recreational nitrous oxide use in an emergency mental health setting.

## Key findings

- Recreational nitrous oxide use was associated with psychotic symptoms in nearly half of the patients.
- Over a third of patients exhibited suicidal ideation or self-harm linked to nitrous oxide use.
- Neurological symptoms like paraesthesia and ataxia were observed in a significant minority of cases.

## Abstract

Background/Objectives: Nitrous oxide (N2O), commonly known as laughing gas, is increasingly being used recreationally. While neurological risks are recognized, psychiatric effects remain underexplored. This study investigates neuropsychiatric presentations among patients referred to the Emergency Mental Health (EMH) team at Sunshine Hospital, Melbourne, Australia, associated with recreational N2O use. Methods: We conducted a retrospective observational review of EMH referrals between August 2020 and July 2024. Inclusion criteria were patients with documented recreational N2O use within the preceding 12 months. Cases were operationally defined as presenting with either predominantly psychiatric features (psychosis or suicidal ideation/self-harm documented by clinician) or predominantly neurological features (ataxia, paresthesia, pyramidal signs, or other focal deficits). Primary outcomes included type and severity of neuropsychiatric presentation, concurrent substance use, and disposition from the Emergency Department. Results: Of 25 identified patients, 23 met inclusion criteria (12 males, 11 females; mean age 29.3 ± 8.3 years). Psychotic symptoms were reported in 11/23 (47.8%, 95% CI 27.3–69.0) and suicidal ideation or self-harm in 8/23 (34.8%, 95% CI 17.2–55.7). Neurological symptoms, including paraesthesia and ataxia, occurred in 5/23 (21.7%, 95% CI 7.5–43.7). Concurrent substance use was documented in 19/23 (82.6%, 95% CI 61.2–95.0), most frequently cannabis, alcohol, and tobacco. Over half of patients (12/23; 52.2%, 95% CI 30.6–73.2) identified as culturally and linguistically diverse (CALD). Conclusions: Among EMH-referred ED patients, recreational N2O use is associated with a spectrum of neuropsychiatric presentations, including psychosis, suicidality, and neurological symptoms. These findings reflect clinical associations rather than causal relationships and highlight the need for early recognition, targeted assessment, and appropriate follow-up in high-risk patients.