Laughing Gas Illustration (image) Washington University School of Medicine Share Print E-Mail Caption Nitrous oxide (laughing gas) has been used as an anesthetic in medicine and dentistry for 150 years. In this illustration from a 19th century book, a man is shown dancing after inhaling the gas. Now, researchers at Washington University School of Medicine in St. Louis are evaluating nitrous oxide as a treatment for depression. Credit Wellcome Library, London. Wellcome Images Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.