If someone with multiple personalities threatens to kill themselves is it considered a hostage situation?

It is important to note that multiple personality disorder is no longer recognized as a legitimate diagnosis in the field of psychology or psychiatry. Instead, the current understanding of these cases falls within the spectrum of dissociative disorders. With that clarification in mind, let's address your question:

A situation in which someone threatens suicide generally does not constitute a hostage situation. A hostage situation typically involves an individual holding one or more people against their will, using threats or force to maintain control. In the case you described, the individual appears to be potentially considering self-harm rather than holding others hostage.

Suicide threats should always be taken seriously, and professional intervention is crucial. It is essential to reach out to mental health professionals, crisis support services, or local emergency services to ensure the individual receives the necessary support and assistance.

If the individual is presenting an imminent threat to themselves or others, it is important to involve appropriate authorities who can intervene safely and effectively. The primary focus should be on de-escalating the situation, providing psychological support, and preventing harm to the individual and those around them.