A severely depressed patient has made an unusual claim about his own body. Before revealing the answer, decide how you would explore whether this is a nihilistic delusion.

Ask the patient to explain the belief in his own words, and establish whether it is held as literal fact, with no acknowledgement that it might be a subjective feeling rather than genuine physical absence, since this total, unshakeable conviction is central to the concept. Ask whether the belief extends outward beyond his own body to other people or the world itself having ceased to exist, and screen specifically for an accompanying delusion of enormity, a belief that a routine action could bring about a vast, catastrophic consequence, since this adds a distinct catastrophic quality when present. Given its most classic association with severe, agitated depression, assess mood state and depressive severity carefully, while also considering schizophrenia and delirium as other recognised contexts.