Research report A comparison of schizophrenia, schizoaffective disorder, and bipolar disorder: Results from the Second Australian national psychosis survey Serafino G. Mancuso a,b,n , Vera A. Morgan c , Philip B. Mitchell d,e , Michael Berk a,f,g,h , Allan Young i , David J. Castle a,b a St Vincent's Mental Health, Fitzroy, VIC, Australia b Department of Psychiatry, the University of Melbourne, Parkville, VIC, Australia c Neuropsychiatric Epidemiology Research Unit, School of Psychiatry and Clinical Neurosciences, The University of Western Australia, Crawley, WA, Australia d School of Psychiatry, University of New South Wales, Sydney, NSW, Australia e Black Dog Institute, Sydney, NSW, Australia f IMPACT Strategic Research Centre, Deakin University, School of Medicine, Barwon Health, Geelong, VIC, Australia g Orygen Youth Health Research Centre, Parkville, VIC, Australia h Florey Institute for Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia i Centre for Affective Disorders, Institute of Psychiatry, King's College London, London, United Kingdom article info Article history: Received 26 June 2014 Received in revised form 18 September 2014 Accepted 21 September 2014 Available online 30 September 2014 Keywords: Schizophrenia Schizoaffective disorder Bipolar disorder Comparison Phenomenology abstract Introduction: It remains uncertain whether schizoaffective disorder (SAD) is a discrete diagnostic entity, is a variant of either a psychotic mood disorder such as bipolar disorder (BDP) or schizophrenia (SCZ), or exists on a spectral continuum between these disorders. The present study examined whether SCZ, SAD, and BDP differed qualitatively on demographic and clinical variables based on a large Australian dataset. Methods: This study examined data from the Australian Survey of High Impact Psychosis (SHIP), in which 1469 of the 1825 participants in who had an ICD-10 diagnosis of SCZ (n ¼857), SAD (n ¼293), and BDP (n ¼319) were assessed across a broad range of variables. Results: When compared to patients with SCZ, those with SAD reported more current delusional and thought disorder symptoms, a greater number of lifetime depression, mania, and positive symptoms, and fewer negative symptoms. Relative to the BPD group, the SAD group were younger, endorsed more current positive, delusional, and thought disorder symptoms, fewer lifetime mania symptoms, more lifetime psychotic, hallucination, and delusional symptoms, and recorded lower premorbid IQ scores. Compared to patients with BPD, those with SCZ were significantly younger, endorsed more current psychotic and hallucination symptoms, fewer lifetime depression and mania symptoms, more lifetime psychotic, hallucination, and delusional symptoms, reported more negative symptoms and had lower premorbid IQ and psychosocial functioning scores. Limitations: Validated psychometric measures of psychotic or mood symptoms were not used. Conclusion: This pattern of results is consistent with the conceptualisation of a spectrum of disorders, ranging from BDP at one end, to SAD in the middle, and SCZ at the other end. & 2014 Elsevier B.V. All rights reserved. 1. Introduction There is ongoing debate in the literature about whether schizoaffective disorder (SAD) is a distinct diagnostic entity, a variant of either schizophrenia (SCZ) or psychotic mood disorders or lies on a continuum between them (Cheniaux et al., 2008; Lake, 2012). The continuum model has been conceptualised as a spectrum of psychotic disorders with mood disorders, including bipolar disorder (BD) with psychotic features (BDP), at one pole and SCZ at the other pole with SAD in the middle (Kempf et al., 2005; Lake and Hurwitz, 2007). Reports of substantial and overlapping heritability estimates for SCZ, SAD, and BD provide support for the continuum model (Cardno et al., 2002). Lichtenstein et al. (2009) found that first- degree relatives of persons with SCZ or BD were at increased risk of these two disorders. Valles et al. (2000) showed that relatives of probands with BD have an increased risk of SCZ, whereas relatives of probands with SCZ have an increased risk of BD. The authors concluded that psychosis may be a nonspecific indicator of illness severity that is not limited to schizophrenia. Comparable results were reported in a meta-analysis by Van Snellenberg (2009), who found that relative to first-degree relatives Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jad Journal of Affective Disorders http://dx.doi.org/10.1016/j.jad.2014.09.035 0165-0327/& 2014 Elsevier B.V. All rights reserved. n Corresponding author at: St Vincent's Hospital46 Nicholson Street PO Box 2900, Fitzroy, VIC 3065, Australia. Tel.: þ61 3 9231 4577; fax: þ61 3 9231 4802. E-mail address: sam.mancuso@svha.org.au (S.G. Mancuso). Journal of Affective Disorders 172 (2015) 30–37