The consumption of cannabis and its links to the development of psychosis has become increasingly important given recent trends towards legalization for medicinal and recreational use. A steady output of scientific research over the past three decades has markedly increased our understanding of cannabis and psychosis. However, media reports usually fail to address the importance of both replication of results and the degree of convergence of results arising from different approaches to the issue. The development of psychotic disorders tends to first occur in adolescence or early adulthood, a developmental period when cannabis use also tends to begin. Early psychosis intervention programs need to be well informed of the key understandings and controversies concerning cannabis, since they are at the leading edge of interventions provided by the mental health system.