Efficacy of Cannabidiol in the Management of Self-injuries in Children and Adolescents With Severe Neurodevelopmental Disorders.

Inclusion Criteria: 1. Age between 5 years and 17 years 6 months; 2. Weight between 12 and 49.9 kg; 3. Clinical diagnosis of severe neurodevelopmental disorder including severe to profound intellectual developmental disorder, characterized in the DSM-5 by a need for help with any daily activity (meals, dressing, toileting, elimination) and the need for constant supervision; 4. Severe self-injuries during the last 7 days defined by BPI-01, i.e.: 1. at least one type of self-injuries assessed as severe intensity occurring at least once every 3 hours while awake or 2. at least two types of self-injuries assessed as severe intensity occurring at least once every 6 hours each while awake; 5. Self-injuries refractory to treatment with atypical neuroleptic (RISPERIDONE, ARIPIPRAZOLE, etc.) at a dosage deemed effective by the investigator in view of the patient's weight, age and background, for a minimum duration of 30 days (except in the case of poor tolerance by the patient); 6. No change in drug and non-drug treatments such as rehabilitative care (psychomotricity, occupational therapy, speech therapy, intervention by a specialist educator) for at least one month; 7. In WOCBP and with active sexual life: negatives hCG and use of highly effective contraceptive measure until 18 days after the end of the treatment. 8. The participant has a caregiver who can reliably accompany him/her to all clinic visits, provide reliable assessments, help him/her to comply with study requirements, and interact with him/her on a regular basis. 9. Signature of Consent of both holders of parental authority; 10. Affiliation to social security regimen. Exclusion Criteria: \- 1. Underweight corresponding to a body mass index below the IOTF 18.5 curve on the International Obesity Task Force's body mass index curves for girls and boys 2. Hypersensitivity to the active substance (cannabidiol) or to any of the excipients (refined sesame oil, anhydrous ethanol, sucralose, strawberry flavor, benzyl alcohol); 3. Treatment with or consumption of cannabidiol in the 12 weeks prior to inclusion; 4. Consumption of cannabis in the 12 weeks prior to inclusion; 5. Usual treatment (excluding treatment of self-injuries) containing molecules interacting with cannabidiol (rifampicin, carbamazepine, enzalutamide, mitotane, St. John's wort, clobazam, valproate, stiripentol, phenytoin, lamotrigine, everolimus, theophylline, tizanidine, bupropion, efavirenz, diflunisal, propofol, fenofibrate, gemfibrozil, morphine, lorazepam, repaglinide, warfarin, sirolimus, tacrolimus, digoxin); 6. Elevated transaminases \> 3N or total bilirubin \> 2N; 7. Known current heart failure; 8. Known current terminal renal failure (GFR \< 15 ml/min/1.73 m2); 9. Known current moderate or severe hepatic insufficiency (Child-Pugh B or C); 10. Known current epilepsy or history of epilepsy, even stabilized, requiring treatment currently or not, whatever the type; 11. Pregnancy or breastfeeding; 12. Inability of the patient or entourage to comply with the study protocol; 13. Patient currently participating in another interventional research (category 1 or 2), clinical trial or clinical investigation, or who are in the exclusion period following him/her participation in another study of this type, as defined in the protocol of that study. 14\. Participant related to a person involved in the study at the investigational site