Caffeine consumption and schizophrenia: a systematic review and meta-analysis of cognitive, symptomatic and functional outcomes

Abstract Background Schizophrenia is a complex mental disorder characterized by cognitive deficits, persistent symptoms, and functional impairment. Caffeine, a commonly consumed psychoactive substance, has plausible effects on cognition and mood. However, its impact on individuals with schizophrenia remains unclear. This review evaluates caffeine’s impact on cognition, symptomatology, and functional outcomes in schizophrenia. Method A systematic literature search was conducted for articles published up to 30 December 2024 across PubMed, Cochrane Library, PsycINFO, Embase, Emcare, and Medline. We included English-language studies in adults with schizophrenia that compared different caffeine intake levels and reported outcomes on cognition, symptoms, or functioning. Cohort, cross-sectional, and clinical trial designs were included. Data were synthesized using a random-effects model with Hedges’ g for effect size and I² statistics for heterogeneity. Results Of 252 articles screened, eleven studies (n=1,406) met inclusion criteria. Findings were mixed. Some studies reported improvements in cognitive performance and working memory, while others observed increases in positive symptoms or inconsistent associations with overall symptom management. Meta-analyses revealed a non-significant increase/decrease in overall symptom severity (measured with Brief Psychiatric Rating Scale (BPRS) and Nurses’ Observation Scale for Inpatient Evaluation (NOSIE). Physiologically, caffeine was found to reduce cerebral blood flow, with no statistically significant effects on blood pressure or pulse. Conclusion Caffeine may have mixed effects on schizophrenia, with potential positive effects on cognitive and negative symptoms while possibly worsening positive symptoms. Functional and physiological impacts are unclear, warranting further research to guide clinical recommendations.