The most prevalent mental illness worldwide and the main contributor to suicide and disability is major depressive disorder. Major depressive disorder is now diagnosed and treated based on the patient's statement of symptoms, mental status tests, and clinical behavioral observations. The central element of this review is the increased need for an accurate diagnostic method. In this context, the present research aims to investigate the potential role of two non-coding RNA species (microRNA and long non-coding RNA) in peripheral blood samples and brain tissue biopsy from patients with major depressive disorder. This study reviewed the literature on microRNA and long non-coding RNA expression in blood and brain tissue samples in human and animal depression models by retrieving relevant papers using the PubMed database. The results reveal significant variations in microRNA and long non-coding RNA levels in depressed patients, making it a crucial diagnostic tool that predicts treatment outcomes. It can help track severe cases and adjust therapy dosages based on treatment responses. In conclusion, microRNAs and long non-coding RNAs are pertinent biomarkers that can be added to the diagnostic test panel for major depressive disorder. Both microRNAs and non-coding RNAs can also be used as a tool to track patient progress during therapy and to assist the attending physician in tracking the molecular development of the disease.
Keywords: biomarker; depression; mammalian models; prognosis; therapy.