A population-based cross-sectional study of cognitive deficits in paranoia

This study sought to investigate the association between paranoia and performance in a range of neurocognitive domains using a large community sample. We conducted a cross-sectional survey of 4507 individuals within the PISMA-ep Study. We used a large community sample selected after multistage sampling using standard stratification techniques. Socio-demographic variables such as age, gender, educational level, urbanicity, and geographical region were recorded. The Spanish version of the Green Paranoid Thought Scale (S-GPTS) was used to assess paranoid thoughts. The Screening for Cognitive Impairment in Psychiatry (SCIP) was used to assess neurocognitive performance both globally and by domains (i.e., immediate and delayed verbal learning, working memory, verbal fluency and processing speed). Individuals with high S-GPTS paranoia scores showed significantly lower performance on global cognitive function and also on immediate (but not delayed) verbal learning, working memory, verbal fluency and processing speed. These results held statistical significance even after controlling for the effects of education and estimated IQ. We propose that cognitive deficits may be mediators of paranoid thinking formation and need to be considered when assessing patients with high levels of paranoia.