Exploratory study about the relationship between leukocytosis and mental disorders in psychiatric outpatients

Elevated levels of inflammatory cytokines and white blood cells (WBCs) have been observed in some patients with psychiatric disorders. However, the prevalence of leukocytosis, its association with psychiatric conditions, and its relevance in psychiatric outpatient care remain underexplored. This study included psychiatric outpatients who visited Akebono Clinic and underwent blood testing between October 2022 and September 2023. From patient records, we obtained age, sex, DSM-5-TR classification, and the highest and lowest WBC counts during the observation period. Leukocytosis was defined as an absolute WBC count exceeding 10,000 cells/μL. Among the 1120 psychiatric outpatients included, 187 (16.7%) exhibited leukocytosis at least once during their visits. Ten (5.7%) of the 176 patients who underwent blood testing only once had leukocytosis. This percentage was significantly higher than that reported for the general Japanese population ( P  < .001). Leukocytosis exceeded 20% for patients with schizophrenia spectrum, bipolar and related, obsessive-compulsive and related, and personality disorders. The percentages were moderate (between 10% and 20%) for those with sleep-wake, depressive, anxiety, and neurodevelopmental disorders, and low (<10%) for patients with somatic symptom and related, trauma- and stressor-related, and neurocognitive disorders. Leukocytosis had significantly higher percentages for those with schizophrenia spectrum, bipolar and related disorders, and depressive disorders than those for neurocognitive disorders ( P  < .01, P  < .05, and P  < .05, respectively). Leukocytosis was observed in 20.5% of patients aged 30 to 69, 9.5% of those aged 10 to 29, and 8.7% of those aged 70 to 95, indicating significant differences in age groups. Leukocytosis was considerably more frequent in psychiatric patients than in the general population. Its prevalence was especially high, exceeding 20%, in patients with schizophrenia spectrum, bipolar and related, obsessive-compulsive and related, and personality disorders, and among middle-aged individuals.