Research shows that compared with people with a single disorder, people with dual diagnosis have higher rates of: severe illness course and relapse; violence, suicidal behaviour and suicide; and infections and physical health problems. Young people with dual diagnosis are particularly at risk of experiencing poor outcomes. Emerging adulthood is the age period when prevalence is highest for most types of drug use. Young people with dual diagnosis are particularly at risk of experiencing poor outcomes. While there’s no isolated data collected on nitrous oxide use in Australia, recent use of inhalants (including nitrous oxide) has been gradually increasing—from 0.4% in 2001 to 1.7% in 2019, used by more than 60 per cent of people aged 14 years and older. The 2021 Global Drug Survey also lists it as the 13th most popular recreational drug in the world. Nitrous oxide has a number of neuropsychiatric and medical sequelae, including upper and lower motor neurone involvement and psychosis. Clinicians need to be well equipped to provide psychoeducation to young people regarding the risks of nitrous oxide. This case study explores the presentation of a 24 year old male who presented to the Emergency Department with a 3 month history of decline in mental state and neurological symptoms on the background of nitrous oxide use.