Is the Behavioural Inhibition System the core vulnerability for cluster C personality disorders?

The aim of the present study was to determine if Behavioural Inhibition System (BIS) functioning, as described by Gray (Gray, J.A.C. (1982). The Neuropsychology of anxiety: an enquiry into the functions of the Septo-Hippocampal system. Oxford: Oxford University Press), would be a core vulnerability for cluster C personality disorders (PD), that is, if these patients would show a higher anxiety trait (i.e. in Gray's terms) than patients with other PD or without Axis II disorders. A total sample of 77 out-patients was assessed with the Eysenck Personality Questionnaire, Sensitivity to Punishment and Sensitivity to Reward Scales, Karolinska Scales of Personality, and the Structured-Interview for DSM-III-R Personality Disorders (SCID-II). Analyses were conducted considering the following groups: presence of cluster C personality disorder/s, presence of clusters A/B personality disorder/s, absence of personality disorder (non-PD). As a second step, cluster C and non-PD groups were also subdivided according to the presence/absence of anxiety or affective Axis I symptoms. Overall, results showed higher scores on anxiety trait-related scales in the cluster C group. However, only Somatic Anxiety, Psychasthenia and Sensitivity to Punishment scales (SP) clearly distinguished cluster C from each one of the other two groups. After a second analysis, only the Sensitivity to Punishment scale showed independence from Axis I status while discriminating between cluster C and non-PD patients. Results were similar when only behavioural items from the SP scale were considered. From these results we can conclude that a higher BIS functioning would differentiate cluster C personality disorders from patients with other PD or without PD, and that considering only the behavioural anxiety component in their assessment, a low Axis I influence is obtained