Evaluation of Membrane Phospholipid and Energy Metabolism in Subjects at High Risk of Psychotic Transition

Inclusion Criteria for the UHR group: * Patient between 15 and 25 years old * Patient fulfilling the UHR criteria objectified by the Comprehensive Assessment of At Risk Mental State scale (CAARMS) and by the social and professional functioning assessment scale (SOFAS) (the "Vulnerability" group is also taken into account, combining first-degree history and functional impact.) * Patient with no contraindication to performing a 7T MRI examination * Affiliated patient or beneficiary of a social security scheme. * Free, informed consent, written and signed by the participant, the investigator and the legal representative if applicable (at the latest on the day of inclusion and before any examination required by the research). Inclusion Criteria for the Control group: * Subjects aged 15 to 25 years old, * healthy volunteer subject or subject to benefit from an imaging examination, not presenting the criteria of a mental health disorder objectified by a medical interview * Subject with no contraindication to performing a 7T MRI examination * Affiliated subject or beneficiary of a social security scheme. * Free, informed and written consent signed by the participant, the investigator and the legal representative if applicable (at the latest on the day of inclusion and before any examination required by the research). Exclusion Criteria for the UHR group: * Patient not at risk or already in a psychotic pathological process according to DSM-5 criteria. * Patient already receiving antipsychotic treatment or whose background treatment was changed less than a month ago. * Patient presenting an absolute contraindication to 7T MRI such as: foreign bodies (intracranial clips, vascular magnetic clips, cardiac or neural pacemakers, stents, coils, implantable chamber, intracorporeal metallic splinters, cochlear implants, intracorporeal metallic foreign bodies, mechanical heart valve, implanted injection pump, non-removable piercings), pregnant woman, allergy to contrast products, moderate to severe renal insufficiency, breastfeeding, implanted contraception, tinnitus, claustrophobia and braces. The relative contraindications are to be considered, namely: previous surgical interventions, medically implanted device, tattoo or permanent make-up. Exclusion criteria for the control group: \- Subject presenting an absolute contraindication to 7T MRI such as: foreign bodies (intracranial clips, vascular magnetic clips, cardiac or neural pacemakers, stents, coils, implantable chamber, intracorporeal metallic fragments, cochlear implants, intracorporeal metallic foreign bodies, valve mechanical heart, implanted injection pump, non-removable piercings), pregnant woman, allergy to contrast products, moderate to severe renal insufficiency, breast-feeding, implanted contraception, tinnitus, claustrophobia and braces. The relative contraindications are to be considered, namely: previous surgical interventions, medically implanted device, tattoo or permanent make-up.