© 2014 COPYRIGHT PHYSICIANS POSTGRADUATE PRESS, INC. NOT FOR DISTRIBUTION, DISPLAY, OR COMMERCIAL PURPOSES. 349 J Clin Psychiatry 75:4, April 2014 CME Background Articles are selected for credit designation based on an assessment of the educational needs of CME participants, with the purpose of providing readers with a curriculum of CME articles on a variety of topics throughout each volume. Activities are planned using a process that links identified needs with desired results. To obtain credit, read the article, correctly answer at least 70% of the questions in the Posttest, and complete the Evaluation. The Posttest and Evaluation are available at PSYCHIATRIST.COM (Keyword: April). CME Objective After studying this article, you should be able to: • Reassess diagnosis over time in patients with cannabis- and stimulant-induced psychotic episodes Accreditation Statement The CME Institute of Physicians Postgraduate Press, Inc., is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. Credit Designation The CME Institute of Physicians Postgraduate Press, Inc., designates this journal-based CME activity for a maximum of 1 AMA PRA Category 1 Credit™. Physicians should claim only the credit commensurate with the extent of their participation in the activity. Note: The American Academy of Physician Assistants (AAPA) accepts certificates of participation for educational activities certified for AMA PRA Category 1 Credit™ from organizations accredited by ACCME or a recognized state medical society. Physician assistants may receive a maximum of 1 hour of Category I credit for completing this program. Date of Original Release/Review This educational activity is eligible for AMA PRA Category 1 Credit™ through April 30, 2017. The latest review of this material was March 2014. Financial Disclosure All individuals in a position to influence the content of this activity were asked to complete a statement regarding all relevant personal financial relationships between themselves or their spouse/partner and any commercial interest. The CME Institute has resolved any conflicts of interest that were identified. In the past year, Alan J. Gelenberg, MD, Editor in Chief, has been a consultant for Allergan, Forest, and Zynx Health; has received grant/research support from Pfizer; and has been a stock shareholder of Healthcare Technology Systems. No member of the CME Institute staff reported any relevant personal financial relationships. Faculty financial disclosure appears at the end of the article. The Impact of Cannabis and Stimulant Disorders on Diagnostic Stability in Psychosis Grant E. Sara, MM; Philip M. Burgess, PhD; Gin S. Malhi, MD; Harvey A. Whiteford, MD; and Wayne C. Hall, PhD ABSTRACT Background: Substance abuse adds to diagnostic uncertainty in psychosis and may increase the risk of transition from brief and affective psychoses to schizophrenia. This study examined whether comorbid substance disorder was associated with diagnostic instability and progression from other psychosis diagnoses to schizophrenia and whether effects differed for cannabis and stimulant-related disorders. Method: We identified 24,306 individuals admitted to hospital with an ICD-10 psychosis diagnosis between 2000 and 2011. We examined agreement between initial diagnosis and final diagnosis over 2–5 years and predictors of diagnostic change toward and away from a final diagnosis of schizophrenia. Results: Nearly half (46%) of participants with initial brief, atypical, or drug- induced psychoses were later diagnosed with schizophrenia. Persisting illicit drug disorders did not increase the likelihood of progression to schizophrenia (OR = 0.97; 95% CI, 0.89–1.04) but increased the likelihood of revision of index psychosis diagnosis away from schizophrenia (OR = 1.55; 95% CI, 1.40–1.71). Cannabis disorders predicted an increased likelihood of progression to schizophrenia (OR = 1.12; 95% CI, 1.01–1.24), while stimulant disorders predicted a reduced likelihood (OR = 0.81; 95% CI, 0.67–0.97). Stimulant disorders were associated with greater overall diagnostic instability. Conclusions: Many people with initial diagnoses of brief and affective psychoses are later diagnosed with schizophrenia. Cannabis disorders are associated with diagnostic instability and greater likelihood of progression to schizophrenia. By contrast, comorbid stimulant disorders may be associated with better prognosis in psychosis, and it may be important to avoid premature closure on a diagnosis of schizophrenia when stimulant disorders are present. J Clin Psychiatry 2014;75(4):349–356 © Copyright 2014 Physicians Postgraduate Press, Inc. Submitted: November 9, 2013; accepted January 29, 2014 (doi:10.4088/JCP.13m08878). Corresponding author: Grant E. Sara, MM, InforMH, Macquarie Hospital, PO Box 169, North Ryde NSW 1670 Australia (Grant.Sara@health.nsw.gov.au). A person with psychosis may receive different diagnoses over time. “Diagnostic shifts” 1 may reflect interrater variation, changes in available information, the evolution of illness, or a combination of all of these. 1,2 These shifts are of clinical relevance; the diagnosis first made by a person’s treating team may determine his or her subsequent care 3,4 and may shape the expectations of the person, his or her family, and treating clinicians. Comorbid substance use is common in psychosis 5–9 and may contribute to diagnostic shifts in several ways. First, substance use creates clinical uncertainty; it is difficult to judge causation of