Is social function a good proxy measure of personality disorder?

Background: Personality assessment may be helped by proxy measures.

Aims: To examine the assessment of social functioning in relationship to personality disorder.

Method: Secondary analysis of data from three clinical studies, following deliberate self-harm (n = 460), cognitive behaviour therapy for health anxiety (n = 444) and a 30-year follow-up of 200 anxious/depressed patients. Social function and personality were assessed using the Social Functioning Questionnaire (SFQ) and the Personality Assessment Schedule, with its ICD-11 modification. A 5-item short version of the SFQ, the Short Social Functioning Questionnaire (SSFQ), was also developed. The SFQ score in the first two studies (area under curve [AUC] 0.64 and 0.65) partly predicted personality status; in the third study, this achieved close agreement (AUC SFQ 0.85 [95% CI 0.8-0.9]; AUC SSFQ 0.84 [95% CI 0.78-0.89]). In all studies, social function deteriorated linearly with increasing personality pathology. Cut-off points of 4 on the SSFQ and 7 on the SFQ had high sensitivity (SSFQ 82%-90%; SFQ 82%-83%) and acceptable specificity (SSFQ 66%-75%; SFQ 69%-75%) in identifying personality disorder in the third study.

Conclusions: Social functioning recorded in either a 5-item or 8-item self-rating is a useful proxy measure of personality disturbance and may be the core of disorder.