Although the exact etiology of obsessive-compulsive disorder (OCD) is unknown, there is growing evidence of a role for immune dysregulation in the pathophysiology of the disease, especially in the innate immune system including the microglia. To test this hypothesis, we studied inflammatory markers in monocytes from pediatric patients with OCD and from healthy controls. We determined the percentages of total monocytes, CD16+ monocytes, and classical (CD14highCD16−), intermediate (CD14highCD16low), and non-classical (CD14lowCD16high) monocyte subsets in 102 patients with early-onset OCD and in 47 healthy controls. Moreover, proinflammatory cytokine production (GM-CSF, IL-1β, IL-6, IL-8, and TNF-α) was measured by multiplex Luminex analysis in isolated monocyte cultures, in basal conditions, after exposure to lipopolysaccharide (LPS) to stimulate immune response or after exposure to LPS and the immunosuppressant dexamethasone. OCD patients had significantly higher percentages of total monocytes and CD16+ monocytes than healthy controls, mainly due to an increase in the intermediate subset but also in the non-classical monocytes. Monocytes from OCD patients released higher amounts of GM-CSF, IL-1β, IL-6, IL-8, and TNF-α than healthy controls after exposure to LPS. However, there were no significant differences in basal cytokine production or the sensitivity of monocytes to dexamethasone treatment between both groups. Based on monocyte subset distribution and cytokine production after LPS stimulation, patients receiving psychoactive medications seem to have an intermediate inflammatory profile, that is, lower than non-medicated OCD individuals and higher than healthy controls. These results strongly support the involvement of an enhanced proinflammatory innate immune response in the etiopathogenesis of early-onset OCD.

Schizophrenia (SCZ) is a severe, chronic mental disorder of unknown etiology and limited therapeutic options. Bioenergetic deficits in the oxidative phosphorylation system (OXPHOS) during early postnatal brain development may underlie disrupted neuronal metabolism and synaptic signaling, contributing to the neurodevelopmental and behavioral disturbances observed in patients. This narrative review summarizes updated evidence linking mitochondrial-OXPHOS dysfunction to SCZ pathophysiology. The novelty lies in the focus on OXPHOS dysfunction at the enzymatic/functional level, rather than on genetic, transcriptional, or oxidative parameters. While complex I impairment has long been highlighted and proposed as a peripheral marker of the disease, recent studies also report alterations in other OXPHOS complexes and their precursors. These findings suggest that OXPHOS dysfunction is not isolated to a single enzymatic component but affects broader mitochondrial function, alongside oxidative stress, contributing to disease progression through mechanisms involving apoptosis, accelerated aging, and synaptic deterioration. OXPHOS dysfunction in both central and peripheral tissues further supports its relevance to SCZ. Overall, the literature points to mitochondrial OXPHOS abnormalities as a significant biological feature of SCZ. Whether these alterations are causal factors or consequences of disease processes remains unclear. Understanding OXPHOS dysregulation may open new avenues for targeted therapies.

Epigenetic modifications occur sequentially during the lifespan, but their pace can be altered by external stimuli. The onset of schizophrenia and bipolar disorder is critically modulated by stressors that may alter the epigenetic pattern, a putative signature marker of exposure to environmental risk factors. In this study, we estimated the age-related epigenetic modifications to assess the differences between young individuals at familial high risk (FHR) and controls and their association with environmental stressors. The sample included 117 individuals (6–17 years) at FHR (45%) and a control group (55%). Blood and saliva samples were used estimate the epigenetic age with six epigenetic clocks through methylation data. Environmental risk was measured with obstetric complications, socioeconomic statuses and recent stressful life events data. Epigenetic age was correlated with chronological age. FHR individuals showed epigenetic age deacceleration of Horvath and Hannum epigenetic clocks compared to controls. No effect of the environmental risk factors on the epigenetic age acceleration could be detected. Epigenetic age acceleration adjusted by cell counts showed that the FHR group was deaccelerated also with the PedBE epigenetic clock. Epigenetic age asynchronicities were found in the young at high risk, suggesting that offspring of affected parents follow a slower pace of biological aging than the control group. It still remains unclear which environmental stressors orchestrate the changes in the methylation pattern. Further studies are needed to better characterize the molecular impact of environmental stressors before illness onset, which could be critical in the development of tools for personalized psychiatry.