In recent years, increasing popular support for the medicinal and recreational use of cannabis has led to legalization for both medicinal and recreational purposes in the United States. To the extent that these changes in policy lead to increase widespread use, it is important to consider the association between heavy chronic cannabis use and the onset of psychotic illnesses, such as schizophrenia. This article provides a brief review of evidence that support cannabis use as a risk factor in the complex etiology of psychotic illness. In addition to reviewing psychopharmacology, longitudinal research, and clinical studies, the article addresses the potential implications of current research on public health policy.