Insight in nonverbal correlates of paranoid ideation can potentially help improve diagnostic procedures and guide interventions. The aim was to systematically evaluate the scientific evidence investigating nonverbal correlates of paranoid ideation.

The review follows the PRISMA guidelines. Databases PsycINFO, PubMed, Web of Science, and Cinahl were searched for studies concerning the use of standardized instruments for both verbal and nonverbal measurements of paranoid ideation in adult participants. Quality of studies was evaluated using the Effective Public Health Practice Project tool. Data were systematically extracted and summarized thematically and narratively. This review was registered with PROSPERO (CRD42022288001).

The search strategy yielded 3962 results of which 22 papers met inclusion criteria. Half (n = 11) of the included articles included patients with a diagnosis on the psychosis spectrum, the other articles (n = 11) studied healthy populations. Identified nonverbal categories were spatial behavior (n = 6), brain region activity (n = 5), visual perception (n = 5), stress physiology (n = 4), information processing (n = 3), and aggression (n = 1). Some studies investigated multiple nonverbal categories.

Evidence was strongest for spatial behavior and brain region activity as nonverbal correlates of paranoid ideation. Evidence for stress physiology, information processing, and aggression as potential nonverbal correlates was less robust, due to inconsistent findings and small numbers of publications. Using nonverbal methods to assess paranoid ideation requires more investigation and evaluation. The integration of nonverbal assessments might offer new diagnostic possibilities that move beyond traditional verbal methods.