Blink rates in patients with schizophrenia compared to healthy controls:A meta-analysis

Background Eyeblink rates vary with cognitive states and may reflect dopaminergic activity. Early reports have found elevated blink rates in schizophrenia, potentially linked to hyperdopaminergia, but findings have been inconsistent. We performed a systematic review and meta-analysis of blink rates in patients with schizophrenia compared to healthy controls and the impact of medication. Methods We registered a protocol for the review on PROSPERO. We searched PubMed, SCOPUS, and Embase, performed title- and abstract-screening, full-text screening, data extraction, and risk-of-bias assessment. We calculated meta-level effect sizes, assessed effect size heterogeneity, and tested for small-study effects. Results We included 22 studies in the systematic review, of which 19 were included in the meta-analysis, comprising 632 patients and 791 healthy controls. Most studies had a high risk of bias, primarily due to lack of blinding and confounding by medication. Meta-analysis revealed an elevated blink rate in patients with schizophrenia compared to healthy controls (Hedges' g = 0.48; 95 % CI [0.13,0.82]). Stratified meta-analyses revealed elevated blink rates in unmedicated patients with schizophrenia compared with healthy controls (Hedges' g = 0.83; 95 % CI [0.34, 1.31]), but not in medicated patients compared with controls (Hedges' g = −0.09; 95 % CI [−0.64, 0.46]). Conclusion Blink rates are elevated in unmedicated patients with schizophrenia, but not medicated patients compared to healthy controls. These findings underscore further research of the link between blink rates, central dopamine, and schizophrenia.