Cytokines in First-Episode Psychosis: Implications for Pathophysiology: A Narrative Literature Review

Abstract

A pro-inflammatory state, characterized by elevated levels of pro-inflammatory cytokines, is frequently reported among individuals presenting with primary first-episode psychosis (FEP), particularly those with environmental risk factors such as maternal infections and early childhood traumatic experiences. These findings suggest that immune system disturbances may play a crucial role in the onset of psychotic disorders. Building on this, cytokines may contribute to the risk of FEP from the stage of neurodevelopment, where they can induce aberrant changes in neuronal growth. During early childhood, these cytokine-mediated processes may disrupt normal neuronal maturation and lead to brain alterations that increase vulnerability to primary psychotic disorders. Furthermore, pro-inflammatory cytokines exhibit strong bidirectional modulatory interactions with dopamine, a key neurotransmitter implicated in the pathogenesis and persistence of psychosis. Notably, these cytokines may also influence the clinical presentation and severity of psychosis. In addition, antipsychotic medications can partially modulate cytokine levels, and this modulation has been correlated with the efficacy of antipsychotics in treating various psychotic symptoms. Frequently reported cytokines in this context include interleukins (IL-1β, IL-2, IL-4, IL-6, IL-8, and IL-10), tumour necrosis factor-α (TNF-α), and interferon-gamma (IFN-γ). We conducted a non-systematized literature search on Google Scholar and PubMed for studies looking at cytokines in primary psychotic disorders during FEP. In this narrative review, we provide an overview of the literature on immune dysregulation in FEP, with a particular emphasis on cytokines.