Temperament in Schizophrenia and Bipolar disorders – A Meta-Analysis

1. Temperament in Schizophrenia and Bipolar disorders – A Meta-Analysis Jouko Miettunen jouko.miettunen@oulu.fi Department of Psychiatry, University of Oulu, Finland

2. Cloninger’s temperament dimensions • novelty seeking • tendency to respond with intense excitement to novel stimuli and thereby initiating behavior • harm avoidance • tendency to respond intensively to signals of aversive stimuli, thereby stopping behavior • reward dependence • tendency to respond intensely to signals of reward, especially social rewards, thereby continuing particular behaviors • persistence • tendency to persevere in behaviors that have been associated with reward • potential intermediate phenotypes in different psychiatric disorders Cloninger et al. Arch Gen Psychiatry 1993;50:975–90.

3. Meta-analysis • Original studies have not compared temperament between patients with schizophrenia and bipolar disorders • Systematic search of articles using several literature databases • Miettunen et al. Pers Ind Diff 2006;41:1515–26; Compr Psychiatry 2007;48:161–9; Psychiatry Res 2008;160:106–14 • Studies comparing cases (schizophrenia or bipolar disorder) and controls • We found 13 studies on schizophrenia and 9 studies on bipolar disorder

5. Comparisons between cases and controls in bipolar disorders and schizophrenia P=0.061 P=0.048 P=0.037 P=0.147 Effect sizes (Cohen’s d): 0.2-0.5 small, 0.5-0.8 medium, and >0.8 large effect

6. Discussion • The first study to pool case-control studies on schizophrenia and bipolar disorders in temperament • low harm avoidance in bipolar disorders • also when compared to other psychiatric disorders than schizophrenia (e.g. unipolar depression) • low reward dependence in schizophrenia • also when compared to other psychiatric disorders than bipolar disorders • low sociability (negative symptom)

7. Discussion • Previous studies have not found differences between psychotic and non-psychotic bipolar disorders • Engström et al. J Affect Disord 2004;82:131–4 • Overall novelty seeking was low in schizophrenia, high novelty seeking would correlate with substance use • Van Ammers et al. J NervMentDis 1997;185:283–8 • and hallucinations and delusions • Guillem et al. Schizophr Res 2002;56:137–47

8. Future research • Suggestive endophenotypes • Effect of phase of illness • infrequent and missing answers • prodromal phase • Clinical relevance • treatment adherence • substance use • social and clinical outcome www.joukomiettunen.net/presentations