Research report The symptom structure of bipolar acute episodes: In search for the mixing link Isabella Pacchiarotti a,b , Alessandra M.A. Nivoli a,i,j , Lorenzo Mazzarini a,b,h , Georgios D. Kotzalidis a,b , Gabriele Sani b,c , Athanasios Koukopoulos c , Jan Scott d,e,f , Sergio Strejilevich g , Jose ´ Sa ´ nchez-Moreno a , Andrea Murru a , Marc Valentı ´ a , Paolo Girardi b , Eduard Vieta a,n , Francesc Colom a a Bipolar Disorders Programme, Institute of Clinical Neuroscience, Hospital Clı ´nic, Universitat de Barcelona, IDIBAPS, CIBERSAM, Barcelona, Catalunya, Spain b NESMOS Department (Neurosciences, Mental Health, and Sensory Organs), School of Medicine and Psychology, Sapienza University, Rome, Unit of Psychiatry, Sant’Andrea Hospital, Rome, Italy c Centro Bini Roma, Via Crescenzio 42, 00193 Rome, Italy d Academic Psychiatry, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK e FondaMental Foundation, Fondation de Coope´ration Scientifique Hˆ opital A. Chenevier, Creteil, F-94000, France f INSERM, U 955, IMRB, Psychiatry Genetic, Creteil, F-94000, France g Bipolar Disorder Program, Neurosciences Institute, Favaloro University, Ciudad Auto ´noma de Buenos Aires, Argentina h Department of Neuropsychiatry, Villa Rosa, Suore Hospitaliere of the Sacred Heart of Jesus, Viterbo, Italy i Institute of Psychiatry, Department of Neuroscience, University of Sassari, Italy j Rio Hortega contract (CM11/00163), Instituto de Salud Carlos III, Spanish Ministry of Science and Innovation article info Article history: Received 4 July 2012 Received in revised form 11 January 2013 Accepted 11 January 2013 Keywords: Bipolar I disorder Factor analysis Brief Psychiatric Rating Scale Manic episode Major depressive episode Mixed mood episode abstract Objective: The nature of mixed mood episodes is still a matter of controversy amongst experts. Currently, the approach to this syndrome is mainly categorical and very restrictive. The factor-structure of bipolar mood episodes has not been studied yet. We performed a dimensional analysis of the structure of bipolar episodes aimed at identifying a factor deconstructing mixed episodes; furthermore, we analyzed correlations of factors emerging from the factorial analysis of the Brief Psychiatric Rating Scale (BPRS) with Temperament Evaluation of Memphis-Pisa-Paris-San Diego (TEMPS-A) and pre- dominant polarity. Method: 187 consecutive bipolar I inpatients hospitalized for DSM-IV-TR acute mood episodes (depressive, manic or mixed) underwent a standardized assessment, including the 24-item Brief Psychiatric Rating Scale (BPRS 4.0), the 21-item Hamilton Depression Rating Scale (HDRS-21), the Young Mania Rating Scale (YMRS) and the TEMPS-A. Principal factor analysis was performed on BPRS- 24 items. Results: This analysis revealed five factors corresponding to ‘‘psychosis’’, ‘‘euphoric mania’’, ‘‘mixity’’, ‘‘dysphoria’’ and ‘‘inhibited depression’’, capturing 71.89% of the rotated variance. The mixity factor was characterized by higher rates of suicidal ideation, more mixed episodes, higher frequencies of antidepressant (AD) use, depressive predominant polarity and anxious temperament. Discussion: The factor-structure of the BPRS in inpatients with bipolar I disorder with an acute episode of any type is pentafactorial; one factor identified is the mixity factor, which is independent from other factors and characterized by anxiety and motor hyperactivity and by the absence of motor retardation. Our results should prompt reconsideration of proposals for DSM-5 diagnostic criteria for the mixed features specifier. Limitations of the study include the relative small sample, the absence of drug-naı¨ve patients and the use of rating scales no specific for mixed states. & 2013 Elsevier B.V. All rights reserved. 1. Introduction Bipolar disorder is characterized by the alternation of manic, depressive and mixed episodes. In the latter, features of both manic and depressive episodes should occur simultaneously. This categorical view of bipolar disorder does not consider that clinical symptoms across mood episodes tend to cluster together within Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jad Journal of Affective Disorders 0165-0327/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jad.2013.01.003 n Correspondence to: Bipolar Disorders Program, Institute of Neurosciences, Hospital Clinic, IDIBAPS, CIBERSAM, University of Barcelona, Villarroel 170, 08036 Barcelona, Catalonia, Spain. Tel.: þ34 932275400; fax: þ34 932279876. E-mail address: EVIETA@clinic.ub.es (E. Vieta). Please cite this article as: Pacchiarotti, I., et al., The symptom structure of bipolar acute episodes: In search for the mixing link. Journal of Affective Disorders (2013), http://dx.doi.org/10.1016/j.jad.2013.01.003i Journal of Affective Disorders ] (]]]]) ]]]–]]]