Recent studies have revealed an association between history of suicide attempt and inflammatory markers in both the cerebrospinal fluid and the plasma. Post mortem studies have shown an increase in microglial activation in the brain tissue of suicide victims. However the relationship between peripheral and central inflammation in suicide is probably mediated by complex biological processes that are yet elucidated. An increase of blood S100B levels (biomarker of neurovascular damage; PMID 14530574) has been reported in adolescents with suicidal ideation vs. controls and independently of psychiatric disorder.

The investigators hypothesize that peripheral inflammation may alter the blood brain barrier, which normally acts as a filter to ensure proper neuronal functioning, in suicidal patients.

They propose to investigate peripheral inflammation, neurovascular permeability and miRNAs in suicidal behavior pathophysiology as biomarkers of suicidal behavior in depression

150 participants will be enrolled, divided into 3 groups:

• 50 Suicide attempters, i.e. currently depressed patients with a suicide attempt within the 8 last days (with a maximal lifetime number of 3 previous suicide attempts, including the most recent);
• 50 Affective controls, i.e. currently depressed patients without any lifetime history of suicide attempt;
• 50 Healthy controls (age- and gender-matched to patients' groups) with no lifetime history of psychiatric disorders.

The protocol includes two visits for patients (suicide attempters and affective controls) and only one visit (inclusion) for healthy controls.

The first visit is the inclusion visit (Day 0-Day 8). Day 0 is the date of the last suicide attempt for the suicide attempters group and the date of signature of the consent for the affective control and healthy control groups. All the visit exams will be performed within 8 days after Day 0.

The second visit takes place one month +/- one week after inclusion. At each visit, a clinical assessment will be performed to characterise psychopathology and suicidal characteristics. Blood samples will be obtained in order to measure inflammatory markers. An MRI will be performed on order to study white matter microstructure and brain functional connectivity networks.

Common inclusion criteria:

• Aged between 18 and 55 years old,
• Affiliated to a French National Social Security System
• Able to understand the nature, purpose and methodology of the study
• Able to give written informed consent

Specific inclusion criteria

Suicide attempters:

• Subject with a main psychiatric diagnosis of current major depressive episode according to DSM-5 criteria (the existence of psychiatric comorbidities is not a non-inclusion criterion)
• Subject with a recent history of proven suicide attempt (within the 8 days before inclusion)
• Subject with a history of maximum 2 previous lifetime proven SA

Affective controls:

• Subject with a main psychiatric diagnosis of current major depressive episode according to DSM-5 criteria (the existence of psychiatric comorbidities is not a non-inclusion criterion),
• Subject without any lifetime history suicidal behavior (proven, interrupted or aborted)

Healthy controls:

- Subject who have no current or past personal history of psychiatric disorders according to DSM5 criteria.

Non inclusion criteria

• History of psychotic disorders
• Diagnostic of illicit substance / alcohol use disorder within the last 6 months
• Current inflammation-related symptoms including fever and infectious or inflammatory disease
• Severe symptomatic or unstable medical condition (e.g., unstable endocrine or cardiovascular disease)
• Medical disorders affecting CNS function (e.g., history of severe head trauma, epilepsy, tumor)
• Current use of specific medications known to affect the immune system, such as corticosteroids, non-steroid anti-inflammatory drugs, aspirin and statins
• Contraindication to MRI or impossibility to assess, or doubt about a contraindication to the MRI: metallic artificial heart valve, pacemaker, cerebrovascular clips ferromagnetic materials, metallic foreign body that can be mobilized, in particular cerebral or intraocular, prosthesis ferromagnetic, impossibility of absolute immobility in supine position, claustrophobia.
• Vaccination in the last month
• Law protected or deprived of liberty subject
• Pregnant and breastfeeding women
• BMI > 30 kg/m2
• Having reached 6000€ annual compensation for participating to clinical trials
• Being in exclusion period for another study