Attentional and memory bias in persecutory delusions and depression

Previous research has indicated that persecutory delusions and depression may share similar cognitive biases at implicit levels of processing, but differentiate at explicit levels, supporting the theory that paranoia may have a protective function against underlying negative schemata. The study aimed to investigate attentional bias and both implicit and explicit memory biases for personally salient and standardised emotional stimuli in persecutory delusions and depression.

36 participants, with 12 in each group, were interviewed in order to generate personally salient stimuli to be employed within the cognitive tests. Standardised emotional stimuli were additionally employed as a control. Participants completed two probe detection tasks, one including personally salient stimuli and one including standard emotional stimuli. Memory for the stimuli presented in this task was assessed by a free recall task (explicit memory) followed by a word completion task (implicit memory).

On an implicit memory task, both the deluded and depressed groups displayed comparable retrieval of positive and negative words. However, on the explicit memory task, the depressed group demonstrated a bias for negative stimuli, whereas the deluded group demonstrated a bias for positive stimuli. The groups did not demonstrate an attentional bias for personally salient information. However, an attentional bias for standardised emotional stimuli was found in the depressed group, although this was not specific to either negative or positive stimuli.

The results indicate that depression and persecutory delusions may share similar patterns of processing at an implicit level but differentiate at the explicit level, which may be indicative of cognitive avoidance of threatening stimuli in psychosis. However, this does not seem to be a feature of automatic attentional processes in people with persecutory delusions. Implications for further research are discussed.