The Oxford Paranoia Defence Behaviours Questionnaire (O-PDQ): assessing paranoia-related safety-seeking behaviours

Defence behaviours - actions carried out to reduce perceived threat - are an important maintenance factor for persecutory delusions. Avoidance of feared situations and subtle in-situation behaviours reduce opportunities for new learning and are erroneously credited for the non-occurrence of harm; hence inaccurate fears are maintained. In contrast, exposure to feared situations whilst dropping defence behaviours - a key technique of cognitive therapy for paranoia - allows the discovery of new information concerning safety, thereby reducing persecutory delusions.

We aimed to develop for use in research and clinical practice a self-report assessment of paranoia-related defence behaviours.

A 64-item pool was developed from interviews with 106 patients with persecutory delusions, and completed by 53 patients with persecutory delusions, 592 people with elevated paranoia, and 2108 people with low paranoia. Exploratory and confirmatory factor analyses were used to derive the measure. Reliability and validity were assessed.

Two scales were developed: a 12-item avoidance scale and a 20-item in-situation defences scale. The avoidance scale had three factors (indoor spaces, outdoor spaces, and interactions) with an excellent model fit (CFI=0.98, TLI=0.97, RMSEA=0.04, SRMR=0.027). The in-situation defences scale had a 5-factor model (maintaining safety at home, mitigating risk, staying vigilant, preparing for escape, and keeping a low profile) with a good fit (CFI=0.95, TLI=0.94, RMSEA=0.046, SRMR=0.039). Both scales demonstrated good internal reliability, test-retest reliability, and construct validity.

The Oxford Paranoia Defence Behaviours Questionnaire is a psychometrically robust scale that can assess a key factor in the maintenance of persecutory delusions.