Electroconvulsive therapy (ECT) is the treatment of choice for drug-resistant depression (30% of patients), or when there is a short-term risk to the patient's life. Despite its robust efficacy and rapid onset of action, its use is limited both by the limited range of treatment available and by the cognitive effects sometimes induced. The present study focuses on the links between the efficacy of ECT, its cognitive effects and the formation of new neurons in the hippocampus (hippocampal neurogenesis) associated with this treatment.

Inclusion Criteria:

1. Study population: depressed subjects treated with ECT

   • Male or female over 18 years of age
   • Hospitalised at the Centre Hospitalier Sainte-Anne
   • Suffering from a unipolar or bipolar major depressive episode, according to DSM5 criteria
   • Indication for ECT treatment
   • Patient has given informed written consent
   • Beneficiary of a social security scheme

2. Control population: depressed subjects treated without ECT

   • Male or female over 18 years of age
   • Hospitalised at the Centre Hospitalier Sainte-Anne
   • Suffering from a unipolar or bipolar major depressive episode, according to DSM5 criteria
   • Patient who has given informed written consent
   • Beneficiary of a social security scheme

3. Control population: healthy volunteers

   • Male or female over 18 years of age
   • Patient with written informed consent
   • Beneficiary of a social security scheme

Exclusion Criteria:

1. Study population: depressed subjects with ECT

   • Psychiatric comorbidity: schizophrenia, pervasive developmental disorder, dependence on a substance other than tobacco
   • Neurological comorbidity: Parkinson's disease, dementia
   • ECT treatment in the 6 months prior to inclusion
   • Compulsory care
   • Protected adults, persons under court protection measures
   • Persons deprived of liberty by judicial or administrative decision;
   • Refusal of consent to ECT treatment
   • Contraindications to ECT (HTIC, recent history of stroke, severe uncontrolled arterial hypertension, contraindication to anaesthesia)
   • Contraindications to MRI (patients with metal prostheses, claustrophobia)
   • Pregnant or breast-feeding women

2. Control population: depressed subjects without ECT

   • Psychiatric comorbidity: schizophrenia, pervasive developmental disorder, dependence on any substance other than tobacco
   • Neurological comorbidity: Parkinson's disease, dementia
   • ECT treatment in the 6 months prior to inclusion
   • Compulsory care
   • Protected adults, persons under court protection measures
   • Persons deprived of liberty by judicial or administrative decision;
   • Pregnant or breast-feeding women

3. Control population: healthyvolunteers

   • Protected adults, persons under legal protection,
   • Persons deprived of their liberty by judicial or administrative decision ;
   • persons hospitalised for purposes other than research
   • Clear psychiatric history
   • Dependence on any substance other than tobacco
   • Neurological history: Parkinson's disease, dementia
   • Pregnant or breast-feeding women

This study focuses on a population of adult patients suffering from unipolar or bipolar depression and treated with electroconvulsive therapy.

In order to monitor the impact of depression on cognitive functions, including memory, and on biological markers and brain imaging, 35 depressed subjects treated without ECT will be recruited.

And to monitor the effect of time on memory, 35 healthy volunteers will be recruited.