Cerebral Neuroinflammation During Major Depressive Episode

* Inclusion criteria for all groups: * Written agreement for participation * Able to understand instructions and information data * Inclusion criteria for the experimental group: * Responding to MDD criteria (DSM-5) * MADRS score\> 20 * Antidepressant medication considered ineffective and before the introduction of a new treatment according to the recommendations (unchanged dosage for at least a week and plasma levels within the therapeutic range) * Inclusion criteria for the pathological control group : * Having met MDD criteria (DSM-5) * In remission for 8 weeks according to the DSM-5 * MADRS score \<10 * Treated with antidepressants (unchanged dosage for at least week) * Inclusion criteria for the control group : * Without any neurological or psychiatric previous disorder * CRPus \< 5mg/L * Exclusion criteria for all groups: * Patients without public insurance regime. * Specific contraindication to the use of MRI (metallic material) or PET (specific allergy related to the ligand). * Pregnant and breastfeeding women * Persons deprived of liberty by judicial or administrative decision * People hospitalized without consent, or subject to legal protection * Persons unable to consent * Patients with a neurodegenerative disease, bipolar disease, chronic psychotic disorder, addictive disorder, Obsessive Compulsive Disorder, Post-Traumatic Stress disorder (PCL-S\> ou =45), known system pathology * Patients with a history of stroke * Patients with an acute infectious disease * Patients with chronic inflammatory pathology. * Patients treated with anti-inflammatory and/or immunosuppressive, and/or antipsychotics, and/or diazepam * Exclusion criteria for control group: * No significant psychiatric or somatic history. * No psychotropic treatment * Suicidal risk (C-SSRS) * Anxiety Disorders (MINI)