Since February 2016, French Claeys-Leonetti law has recognized patients' right to confront incurable diseases with short-term prognosis and refractory physical or psychological or existential symptoms by requesting continuous deep sedation until death (CDSUD). Determining when psychological or existential distress is refractory and unbearable remains complex and controversial.

This review provides a comprehensive thought on CDSUD for advanced incurable patients with refractory psychological and/or existential distress in palliative care settings. It offers guidance on psychiatric or psychological diagnosis for explaining patients' requests for CDSUD.

A narrative literature review (2000–2019) was conducted on the MedLine search about the use of palliative sedation in cases of refractory psychological and/or existential distress.

(1) Definitions of “refractory symptom,” “refractory psychological distress,” and “refractory existential distress” are inconsistent; (2) alternative diagnoses might obscure or be obscured by psycho-existential distress; and (3) criteria on meanings, reasons for requests, decision-making processes, and functions are evolving in practice.

Before implementing CDSUD, palliative healthcare professionals should seek input from psycho-oncologists in palliative care. Mental health professionals should analyze and assess the reasons for psychological and/or existential distress, consider the intentionality processes of requests, and explore alternative diagnoses, such as depressive or adjustment disorders, demoralization syndrome, desire to hasten death, and desire for euthanasia. Therapeutic responses (e.g., pharmacological and psychotherapeutic) should be implemented before deciding that psycho-existential distress is refractory.