Experimental studies of paranoid thinking in clinical and nonclinical populations: a systematic review and meta-analysis.

Paranoia is common in clinical and nonclinical populations, consistent with continuum models of psychosis. A number of experimental studies have been conducted that attempt to induce, manipulate or measure paranoid thinking in both clinical and nonclinical populations, which is important to understand causal mechanisms and advance psychological interventions. Our aim was to conduct a systematic review and meta-analysis of experimental studies (non-sleep, non-drug paradigms) on psychometrically assessed paranoia in clinical and nonclinical populations. The review was conducted using PRISMA guidelines. Six databases (PsycINFO, PubMed, EMBASE, Web of Science, Medline and AMED) were searched for peer-reviewed experimental studies using within and between-subject designs to investigate paranoia in clinical and nonclinical populations. Effect sizes for each study were calculated using Hedge's g and were integrated using a random effect meta-analysis model. Thirty studies were included in the review (total n = 3898), which used 13 experimental paradigms to induce paranoia; 10 studies set out to explicitly induce paranoia, and 20 studies induced a range of other states. Effect sizes for individual studies ranged from 0.03 to 1.55. Meta-analysis found a significant summary effect of 0.51 [95% confidence interval 0.37-0.66, p < 0.001], indicating a medium effect of experimental paradigms on paranoia. Paranoia can be induced and investigated using a wide range of experimental paradigms, which can inform decision-making about which paradigms to use in future studies, and is consistent with cognitive, continuum and evolutionary models of paranoia.

The relationship between appraisals of voices (auditory verbal hallucinations) and distress in voice-hearers with schizophrenia-spectrum diagnoses: A meta-analytic review.

Cognitive-behavioural models of auditory verbal hallucinations (voices) predict that the interpretation of voices determines the levels of distress experienced by voice-hearers. Examining the contribution of these voice appraisals is central to the delivery of effective psychological interventions for the management of distressing psychotic symptoms. This meta-analysis synthesised evidence from studies that tested the relationship between a range of appraisals and several distress measures (voice-related and emotional distress) in individuals with schizophrenia-spectrum diagnoses. A database search (PsycINFO, PubMed and Web of Science) was conducted for articles published up to August 2020. Twenty-eight eligible studies, comprising of 1497 clinical participants examined the association between eight voice appraisals and distress. Moderate to large summary effects (r ranging between 0.30 and 0.50) were observed in several analyses focusing on 'maladaptive' appraisals and beliefs about voices (malevolence, power, metaphysical beliefs, beliefs about loss of control, voice intrusiveness), with voice dominance having a large summary effect, r = 0.58, 95% CI [0.43, 0.69]. Positive appraisals and beliefs had small negative summary effects on distress. The magnitude of the observed effects was similar across subgroup analyses considering measures of voice-related distress, anxiety and depression. The findings of this evidence synthesis broadly corroborate cognitive-behavioural models of distressing voices, but suggested that factors other than voice appraisals may also predict the distress and impairment caused by hallucinatory experiences in people with schizophrenia-spectrum disorders. Nonetheless, our findings confirm that voice appraisals are an important and meaningful target for treatment in help-seeking voice hearers with psychosis.

Perceived discrimination and psychosis: a systematic review of the literature.

PURPOSE: Higher rates of psychosis have been reported in minority groups. Since individuals belonging to such groups are vulnerable to the experiences of discrimination, and in line with models proposing that social and life adversity may play a causal role in development and maintenance of psychotic experiences, it has been proposed that perceived discrimination may represent an important determinant of psychotic experiences. This paper reviews the literature examining the relationship between perceived discrimination and psychosis, examining whether discrimination is associated with an increased risk of psychosis, the severity of psychotic symptoms and whether there is an association with specific psychotic symptoms. METHODS: A systematic database search of PsycINFO, Embase and PubMed was conducted to identify quantitative cross-sectional and prospective studies that examined the association between discrimination and psychosis. RESULTS: Twenty-four studies met the inclusion criteria, four of which used prospective designs and twenty used cross-sectional designs. The main findings indicated that discrimination may be associated with an increased risk of psychosis (too few studies to determine whether discrimination is associated with severity). Some studies found associations between discrimination and positive psychotic experiences and/or specific psychotic experiences such as paranoia. A small number of studies found that greater exposure to discrimination was associated with a greater likelihood of reporting psychotic experiences, tentatively indicating a dose-response relationship. CONCLUSIONS: This review indicates that discrimination plays an important role in the experience of psychosis; however, future research is required to clarify the nature of this relationship. Avenues for further research and clinical implications are proposed.