• inflammatory processes
• biological markers
• bipolar disorder
• neutrophil-lymphocyte ratio
• platelet-lymphocyte ratio
• lymphocyte-monocyte ratio

 Introduction: Recently, inflammatory processes have been increasingly supposed to be involved in the pathophysiology of mood disorders. Peripheral markers such as neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), lymphocyte-monocyte ratio (LMR) are currently the topic of a deep investigation as inexpensive and reproducible markers of systemic inflammation in many diseases. However, only a few studies are available on the clinical and prognostic value of these ratios in psychiatric disorders. Therefore, the aim of the present study was to investigate the possible clinical value and impact of some inflammatory markers in patients with bipolar disorders (BDs).
Methods and Materials: In this retrospective study, all patients between aged 18 to 65 years who were hospitalized with a diagnosis of Bipolar Disorders at the Psychiatric Clinic, Department of Clinical and Experimental Medicine, at the University of Pisa between 1 June 2019, and 1 June 2020, were evaluated for inclusion criteria. Only those patients with complete blood counts performed within 24 h after hospitalization were included. Patients receiving any anti-inflammatory drugs or suffering from a systemic inflammatory disease that might potentially modify any l inflammatory parameters were excluded from this study. White blood cell, neutrophil, lymphocyte, platelet, and monocyte counts were recorded retrospectively from complete blood count data collected during hospitalization, and NLR, PLR, MLR, LRR, NRR, MRR, PRR, LMR, dNLR, SIRI and AISI values were calculated. Socio-demographic data and clinical characteristics of BD were also retrieved from patient records
Results: Seventy patients aged 18–65 were included in the study. The results showed that NLR, dNLR, NRR, SIRI and AISI were higher in manic / hypomanic patients, as to depressed and euthymic ones. The LRR values were lower in manic / hypomanic subjects. Within the manic / hypomanic group, NLR, dNLR, NRR values were higher in BD I patients. Patients with psychotic features showed higher dNLR, NRR and SIRI. The AISI and PRR values were higher in patients with mixed symptoms. Patients with hyperthymic personality had higher NLR, dNLR, NRR, AISI, SIRI, PLR and lower LRR values, when compared to the rest of the sample. Dysthymic patients presented lower levels of NLR, dNLR, NRR, compared to irritable individuals, and lower NLR, dNLR, NRR, PLR, PRR values compared to cyclothymic ones. The LRR was inversely related to lenght of illness.
Conclusion: The findings of the present study would suggest the importance of a simple blood count, an inexpensive and reproducible exam, in possibly exploring the pathophysiology and course of BDs. Interestingly, although further studies are necessary to confirm these results. some variables could be considered as both state markers for the polarity episode and trait markers for BD patients with hyperthymic personality traits. Taken together, inflammatory peripheral markers seem quite promising to better disentangle the complex relationships between inflammatory / cardiovascular diseases and BDs, and thus, to provide clinical implications in terms of management and novel treatment strategies.