Rational:~Major Depressive Episode (MDE) affects nearly 15% of the general population. To date, its pathophysiology remains unclear and treatment effects are often inconsistent. Therefore, it is challenging to make a valid prognosis for depression and identification of biomarkers is an important way of improving patient's treatment. Messenger RNAs (mRNAs) could be potential biological markers. Several studies have shown quantitative variations in peripheral blood mononuclear cells (PBMC) during MDE. These variations are state dependent and/or correlated with clinical measures.~In a preliminary study, the investigators identified 12 genes whose expression was either altered between patient and control samples and/or between first patient samples and samples from the same patients obtained 8 weeks later. However, this study did not assess evolution of these alterations beyond an 8 weeks window and only 2 time points were considered.~Objective:~the investigators aim to compare gene expression difference for 21 candidate genes, of which 12 were already investigated, in 2 groups of subjects. MDE and control samples will be analyzed across a large time window to draw a better picture of the complex progression during MDE.~Population and method:~This study is longitudinal and comparative. 20 subjects per group will be included and followed during a 6 months interval which includes 4 visits (at the inclusion, 2 and 8 weeks later and finally 6 month later). Clinical observations and psychometric scales will be used for evaluations. Blood collections and PBMCs extraction will be operated after each evaluation and followed by RNA extraction, reverse transcription and gene expression quantification by real-time PCR.~Expected results:~mRNA will be either over or under-expressed in patients during MDE in correlation with the clinical state. There will be no variation across time in control subjects. Comparison between MDE and control will show differences during MDE but not after clinical remission.
Major Depressive Episode (MDE) affects nearly 15% of the general population. In a preliminary study, the investigators identified 12 genes whose expression was either altered between patient and control samples and/or between first patient samples and samples from the same patients obtained 8 weeks later. However, this study did not assess evolution of these alterations beyond an 8-week window and only 2 time points were considered. The investigators aim to compare gene expression difference for 21 candidate genes, of which 12 were already investigated, in 2 groups of subjects. MDE and control samples will be analyzed across a large time window to draw a better picture of the complex progression during MDE.