Treatment Resistance in Psychiatric Disorders: the Search for Biological Markers Predictive of Response to Treatment

The disruption of immune system is a key candidate in the pathogenesis of psychiatric disorders, especially those resistant to traditional treatments. Involving complex processes within the brain and peripheral immune system, inflammation may lead to imbalance of neurotransmitter systems and synaptic plasticity and directly contribute to the psychiatric symptoms observed in conditions such as depression, bipolar disorder (BD) and schizophrenia (SCZ). Studies show that treatment-resistant depression (TRD) is associated with elevated levels of inflammatory markers in the blood, which are linked to a lower response to conventional antidepressants. Interventions that modulate this inflammatory response, such as immunomodulatory treatments or therapies targeting pro-inflammatory cytokines, have demonstrated beneficial effects by reducing symptoms and improving patients' quality of life. A thorough understanding of the links between inflammation and treatment resistance therefore paves the way for innovative therapeutic strategies. These approaches could transform current practices by offering more personalized and effective solutions for patients suffering from chronic and resistant psychiatric disorders.