Neuroinflammation and excitatory symptoms in bipolar disorder

Neuroinflammation has been proposed as a strong biological factor underlying the development of neuropsychiatric diseases. A role for dysregulation of the immune system was initially suggested in depressive disorders and subsequently extended to other illnesses, including bipolar disorder (BD). Indeed, there is growing evidence confirming the presence of a generalized pro-inflammatory state in BD patients, involving alterations in cytokine, acute-phase proteins, and complement factor secretion, white blood cell differentiation, microglial activation, arachidonic acid signaling pathways, and increased oxidative stress markers. Medications commonly used to treat BD, such as lithium, antiepileptics and antipsychotics, show some immunoregulatory activity both in vitro and in vivo. The aim of our study was to review the role of different inflammatory mechanisms, specifically in the development of excitatory symptoms, via a systematic PubMed search of the literature. Despite the high variability of results among studies, we found evidence indicating specific alterations of the inflammatory response during manic and mixed states of BD. These findings may help to clarify some of the complex mechanisms underlying the development of excitatory symptoms and suggest a potential role for drugs targeting the inflammatory system as new therapeutic options