Cognitive impairment and elevated neutrophil-to-lymphocyte ratio and monocyte-to-lymphocyte ratio in schizophrenia

The efficacy of current schizophrenia treatments on cognitive symptoms remains limited owing to constrained data around the aetiopathogenesis of such symptoms. Complete blood cell counts have been used to identify variations in inflammatory responses among individuals with schizophrenia. This study aimed to determine associations between inflammatory markers and cognitive impairment in patients with schizophrenia.

Patients with schizophrenia aged 20 to 40 years were recruited from Prof Dr M Ildrem Hospital, Medan, Indonesia. Diagnoses were made by psychiatrists based on the DSM-5 criteria. Healthy controls matched for age, sex, and body mass index were recruited from the local community. The severity of schizophrenia was assessed by a psychiatrist using the Positive and Negative Syndrome Scale. Cognitive performance was assessed using the Montreal Cognitive Assessment (MoCA). Complete blood cell counts were performed. Absolute neutrophil, lymphocyte, monocyte, and white blood cell (WBC) counts were quantified, and the neutrophil-to-lymphocyte ratio (NLR) and monocyte-to-lymphocyte ratio (MLR) were calculated.

In total, 64 men and 38 women were included in the analysis. Patients with schizophrenia (n = 52) and healthy controls (n = 50) were comparable in terms of all baseline characteristics, except that patients with schizophrenia were older (33.4 vs 27.9 years, p < 0.001) and had lower MoCA scores (16.79 vs 27.60, p < 0.001). For patients, the mean illness duration was 3.5 years, and the mean Positive and Negative Syndrome Scale score was 74.15. Patients with schizophrenia had higher WBC counts (8.89 vs 7.53 10³/μL, p = 0.002), neutrophil counts (6.77 vs 5.05 10³/μL, p < 0.001), and NLR (3.96 vs 2.68, p < 0.001). Neutrophil counts (r = -0.293, p = 0.035), NLR (r = -0.393, p = 0.004), and MLR (r = -0.351, p = 0.011) were negatively correlated with MoCA scores.

Patients with schizophrenia show signs of cognitive impairment and elevated WBC counts, neutrophil counts, and NLR. These peripheral inflammatory markers may be used to enhance understanding of the complex inflammatory theory of psychotic disorders.