Over the last decade in Australia, methamphetamine has come to be seen as a significant issue for drug research, policy and practice. Concerns have been expressed over its potency, the increasing prevalence of its use and its potential for producing greater levels, and more severe forms, of harm compared to amphetamine or other drugs. In this article, we critically examine some of the ways in which methamphetamine and its effects are produced and reproduced within and through Australian public discourse, focusing in particular on the associations made between methamphetamine and psychosis. We show how public discourse enacts methamphetamine as an anterior, stable, singular and definite object routinely linked to the severe psychological 'harm' of psychosis. We contrast the enactment of methamphetamine within public discourse with how methamphetamine is enacted by consumers of the drug. In their accounts, consumers perform different methamphetamine objects and offer different interpretations of the relationships of these objects to psychological problems and of the ontological nature (i.e. relating to what is real, what is, what exists) of these problems. In examining public discourse and consumer accounts, we challenge conventional ontological understandings of methamphetamine as anterior, singular, stable and definite, and of its psychological effects as indicative of pathology. In line with recent critical social research on drugs, we draw on social studies of science and technology that focus on the performativity of scientific knowledge and material practices. We suggest that recognising the ontological contingency, and therefore the multiplicity, of methamphetamine offers a critical counterpoint to conventional research, policy and practice accounts of methamphetamine and its psychological effects.