Speaking of yourself: A meta-analysis of 80 years of research on pronoun use in schizophrenia

People with schizophrenia experience significant language disturbances that profoundly affect their everyday social interactions. Given its relevance to the referential function of language, aberrations in pronoun use are of particular interest in the study of schizophrenia. This systematic review and meta-analysis, adhering to PRISMA guidelines, examines the frequency of pronoun use in schizophrenia. PubMed, PsycINFO, Scopus, Google Scholar, and Web of Science were searched up to May 1, 2024. All studies analyzing pronoun frequency in various spoken language contexts in schizophrenia were included. Bias was assessed using a modified Newcastle-Ottawa Scale. A Bayesian meta-analysis with model averaging estimated effect sizes and moderating factors. 13 studies with n = 917 unique participants and 13 case-control contrasts were included. 37.9 % of patient samples were women, with a weighted mean (SD) age of 34.45 (9.72) years. 53.85 % of the studies were in languages other than English. We report a medium-sized effect for first-person pronoun impairment in schizophrenia (model-averaged d = 0.89, 95 % CrI (0.44, 1.33)). There was significant heterogeneity moderated by age. Evidence for publication bias was weak, with a strong support for first-person pronoun impairment after accounting for bias and heterogeneity. There was a small reduction of inter-individual variability in first-person pronoun use in patients compared to healthy controls (lnCVR = -0.12, 95 % CrI [-0.35, -0.13]). While all pronoun use was also high in patients, this was not robust due to heterogeneity and publication bias. Individuals with schizophrenia excessively use first-person pronouns. This may be a marker of a disturbed sense of self in this illness.