Abstracts of the 4th Biennial Schizophrenia International Research Conference / Schizophrenia Research 153, Supplement 1 (2014) S1–S384 S43 the class with the worst premorbid adjustment and information processing deficits, 74% of the subjects made a transition to psychosis whereas in the lowest risk class only 4% transitioned. Furthermore, in the highest risk class transition emerged on average 17 months earlier than in the lowest risk class. However, transferring our approach into clinical practice requires validation in an independent sample. A successful transfer would provide new opportunities for developing targeted intervention strategies based on a subjects’ individual risk index. References: [1] van der Gaag M, Nieman D, van den Berg D. 2013. CBT for Those at Risk of a First Episode Psychosis: Evidence based psychotherapy for people with an “At Risk Mental State”. Oxford, UK: Routledge. 217p, ISBN 978-0-415-53968-5. [2] van der Gaag M, Nieman DH, Rietdijk J, Dragt S, Ising HK, Klaassen RM, Koeter M, Cuijpers P, Wunderink L, Linszen DH. Cognitive behavioral therapy for subjects at ultra high risk for developing psychosis: A randomized controlled clinical trial. Schizophrenia Bulletin 2012;38:1180–8. [3] Nieman DH, Ruhrmann S, (combined first authorship), Dragt S, Soen F, van Tricht MJ, Koelman JHTM, Bour LJ, Velthorst E, Becker HE, Weiser M, Linszen DH, de Haan L. Psychosis prediction: Stratification of risk estimation with information- processing and premorbid functioning variables. Schizophrenia Bulletin, in press. Symposium CHILDHOOD TRAUMA AS RISK FACTOR IN PSYCHOTICDISORDERS –IN SEARCH OF MECHANISMS Chairperson:Ingrid Melle Discussant: Paola Dazzan Tuesday, 8 April 2014 2:00 PM– 4:00 PM Overall Abstract:Background: Large population based studies demonstrate a link between childhood trauma (CT) and increased prevalence of per- sonality disorders, depression, bipolar disorder and schizophrenia. Existing studies rely on cross-sectional investigations and the potential mechanisms involved in the relationship between CT and the risk of developing a severe mental disorder or important core characteristics are largely unknown. Methods: This symposium brings together recent research on the role of CT from ongoing large studies in Australia, France, the UK and Norway. The findings confirm that there are high rates of CT not only in schizophrenia but also in the ultra-high risk population and inpatients with bipolar disor- der, and underlines the link between CT, disturbances in the stress-response system and potential gene x environment interactions on important clinical phenotypes. Results: Studies of trauma in the UHR population indicate that there are high rates of CT, comparable to rates in clinical populations with established psychotic disorder, and an association between history of sexual trauma and transition to psychotic disorder when other risk factors are controlled for. In bipolar disorder, multiple traumas are more frequently reported in patients compared to controls, with emotional- and sexual abuse appearing to be associated with a more severe expression of the disorder. Individuals exposed to high levels of CT show long term changes in their stress response system, together with cognitive and structural brain changes in regions implicated in cognitive and behavioral regulation. High levels of stress exposure are also linked to suppression of neurogene- sis, possibly mediated by stress-based reductions in neurotrophic factors. Also first-episode patients and healthy controls exposed to CT have an abnormal biological stress response including high diurnal cortisol levels and increased levels of pro-inflammatory cytokines and reduced levels of brain-derived neurotrophic factor (BDNF). Additionally, carriers of the Methionine (met) allele of the BDNF Val66Met polymorphism exposed to high levels of CT demonstrate significantly poorer cognitive functioning and show structural changes in the CNS including reduced right hippocampal volumes and larger lateral ventricles. Discussion: The presented studies confirms the high rate of CT across a broad spectrum of patient groups; underlining the importance of sexual- and emotional abuse, and add to the growing understanding of distur- bances in the biological stress-response system and of gene x environment interactions as mechanisms behind the link between CT and psychosis. HISTORY OF TRAUMA INTHE ULTRA HIGH RISK FOR PSYCHOSIS POPULATION: FINDINGS FROM THE PACE CLINIC Barnaby Nelson 1 , Andrew Thompson 2 , Andreas Bechdolf 3 , Patrick McGorry 4 , Alison Yung 4,5 1 Orygen Youth Health, Melbourne; 2 Division of Mental Health and Wellbeing, Warwick Medical School, University of Warwick, United Kingdom; 3 Klinik für Psychiatrie, Psychotherapie und Psychosomatik, Vivantes Klinikum am Urban, Akademisches Lehrkrankenhaus Charite-Universitätsmedizin Berlin, Germany; 4 Orygen Youth Health Research Centre and Centre for Youth Mental Health University of Melbourne, Australia; 5 University of Manchester Background: There is increasing evidence that childhood trauma is a risk factor for psychotic disorder and negatively impacts symptomatic and func- tional outcomes in people with psychotic disorders. The “ultra high risk” (UHR) for psychosis population provides a valuable population in which to study the relationship between trauma and psychosis because it allows for prospective longitudinal investigation of the relationship between the two variables in a group with a high rate of psychosis onset (about 35% over the medium-long term). This overcomes some of the methodological limitations noted with previous studies (such as the possible influence of psychotic symptoms on recall) and provides a perfectly matched control group (UHR patients who do not develop psychotic disorder). Method: This presentation will focus on research conducted into trauma in the UHR population seen at the PACE clinic, Orygen Youth Health in Melbourne. Results: Studies of trauma in the UHR population seen at the PACE clinic indicate: 1. High rates of trauma (present in approximately 70% of patients), substantially greater than rates in the general population and comparable to rates in clinical populations with established psychotic disorder. 2. An association between history of sexual trauma and transition to psychotic disorder when other risk factors are controlled for. 3. A thematic association between the “content” of attenuated psychotic symptoms and history of sexual trauma. A current study exploring the relationship between trauma, stress reactivity and physiological variables will also be described. Discussion: This research indicates that childhood trauma, particularly sexual trauma, is a risk factor for onset of psychotic disorder in the UHR population, consistent with findings from other centres. Issues that need to be further explored include risk specificity (i.e., whether trauma is a general risk factor for psychiatric disorder or for psychotic disorder particularly); why sexual trauma is associated with higher levels of risk than other types of trauma; the mechanisms by which childhood trauma increases risk for disorder, including the relationship between such life events and physiolog- ical factors, as well as personality and resilience factors; and issues of how childhood trauma can best be addressed therapeutically in this population. CHILDHOOD TRAUMA INFLUENCES THE CLINICAL EXPRESSION OF BIPOLAR DISORDERS Bruno Etain 1,2 , Monica Aas 3 , Frank Bellivier 4 , Ole A. Andreassen 3,5 , Chantal Henry 6,7 , Ingrid Melle 3,5 , Marion Leboyer 8,7 1 Pole de Psychiatrie and Inserm U955, AP-HP, Groupe Hospitalier Henri Mondor, Paris; Fondation Fondamental, Creteil, France France; 2 European Network of Bipolar Research Expert Centres; 3 Institute of Clinical Medicine, University of Oslo, Norway; 4 Service de Psychiatrie et D’Addictologie, Hopital Fernand Widal, Lariboisière, Paris, France; 5 Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway; 6 Pole de Psychiatrie and Inserm U955, Groupe Hospitalier Henri Mondor, Paris, France; 7 Fondation Fondamental, Creteil, France; 8 Pole de Psychiatrie and Inserm, Groupe Hospitalier Henri Mondor, Paris, France Background: The pathophysiology of bipolar disorders (BD) is likely to be partly determined by environmental susceptibility factors that interact with genetic risk variants. Among them, childhood trauma has been proposed as a relevant environmental factor for BD. However, case-controls studies are lacking; most studies focuse only on physical and sexual abuse (thus neglecting emotional abuse), and the influence of trauma on the clinical expression of the disorder remains to be clarified in terms of severity of the course. Methods: First, we have assessed 206 patients with BD and 94 controls with the Childhood Trauma Questionnaire to perform a case/control study.