Cluster analysis of normal personality traits in patients with psychogenic nonepileptic seizures q Dona E. Cragar a, * , David T.R. Berry a , Frederick A. Schmitt b , Toufic A. Fakhoury c a Department of Psychology, University of Kentucky, Lexington, KY, USA b Sanders–Brown Center on Aging, Lexington, KY, USA c Department of Neurology, University of Kentucky, Lexington, KY, USA Received 13 January 2005; revised 28 February 2005; accepted 1 March 2005 Available online 26 April 2005 Abstract The literature on patients with psychogenic nonepileptic seizures (PNES) suggests that they are a heterogeneous population. This study addresses this heterogeneity by describing subtypes of PNES based on a cluster analysis of normal personality traits in patients with PNES. In addition, the identified PNES subtypes are further described on dimensions of psychopathology as measured by the Minnesota Multiphasic Personality Inventory, Second Edition (MMPI-2), and cognition. Three personality clusters emerged: (1) very high neuroticism, low extraversion, low openness, high agreeableness, low conscientiousness; (2) average on all domains; (3) very high neuroticism, average extraversion, low openness, low agreeableness, average conscientiousness. Patients in clusters 1 and 3 appear to exhibit more severe psychopathology and a broader range of symptoms than those in cluster 2. Based on NEO- PI-R and MMPI-2 findings, tentative descriptions of the clusters are offered. Cluster 1 comprises ‘‘depressed neurotics’’; cluster 2, ‘‘somatic defenders’’; and cluster 3, ‘‘activated neurotics.’’ Clusters 1 and 3 also differ significantly on neurocognitive testing, with cluster 1 significantly lower than cluster 3 in memory functioning, while cluster 2 individuals show generally average cognition across domains. These results suggest the existence of personality subtypes in patients with PNES that should be considered in the design of interventions for them. Ó 2005 Elsevier Inc. All rights reserved. Keywords: Psychogenic nonepileptic seizures; Normal personality; Psychopathology; Neuropsychological results; Intervention 1. Introduction Psychogenic nonepileptic seizures (PNES) can be operationally defined as episodes of altered movement, sensation, or experience overtly similar to epilepsy, but caused by a psychological process and not associated with abnormal electrical discharges in the brain [1]. PNES are often considered a somatoform disorder [2], and the common feature of all somatoform disorders is the presence of physical symptoms that suggest a gen- eral medical condition and are not fully explained by a general medical condition. Prevalence estimates of PNES vary widely, from 5% in an outpatient epilepsy clinic up to 33% of patients referred to epilepsy monitor- ing units [3–5]. As recent reviews illustrate [6,7], research has at- tempted to differentiate patients with epilepsy from pa- tients with PNES using a variety of methods [8–10]. Despite the plethora of research on methods for differen- tiating PNES from epilepsy, simultaneous video/EEG monitoring unquestionably remains the gold standard for differential diagnosis [11,12]. There is however, little literature on efficacious treatment strategies for PNES 1525-5050/$ - see front matter Ó 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.yebeh.2005.03.007 q Portions of these data were presented as a poster at the 58th annual meeting of the American Epilepsy Society, New Orleans, LA, USA, December 3–8, 2004. * Corresponding author. Present address: Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. E-mail address: cragar.dona@mayo.edu (D.E. Cragar). www.elsevier.com/locate/yebeh Epilepsy & Behavior 6 (2005) 593–600