I welcome the excellent paper by Guimarães et al. which extends research on nitrous oxide (N2O) in neuropsychiatry – a neglected field, since our initial work in 1982 and then 1985 indicating that low, anxiolytic, and non-anaesthetic doses of N2O ameliorate depression. 3 Research has demonstrated that N2O, at subanaesthetic concentrations acts on opioid receptors. We therefore concluded that...