Vertaling van "which he she forms " (Nederlands → Frans) :

It is crucial to take advantage of the moment of crisis and the moment at which the suicidal act is being carried out to make extensive use of the issues of the patient as well as those of the whole system of which he/she forms a part.
Il est capital de profiter du moment de crise et de passage à l’acte suicidaire pour mobiliser de manière intensive la problématique du patient mais aussi de tout le système dans lequel il s’intègre.

It is existential because it has to do with the subject’s entire existence, the way in which the latter lives through it and in which he/she experiences the relationship with the social, emotional, and professional environment.
Existentiel parce que le problème touche à l’ensemble de l’existence d’une personne et concerne la manière dont elle se vit et vit sa relation à son environnement social, affectif, professionnel.