A psychiatric hospital stay often begins with an emergency room visit, though sometimes can be arranged in advance.
There are different reasons for a hospital stay:
-a high or immediate risk of suicide
-inability to safely care for self at home
-diagnostic uncertainty with serious symptoms requiring a more urgent, comprehensive medical evaluation (e.g. delirium)
-behaving dangerously due to psychiatric symptoms (e.g. a manic state)
-initiating a treatment that is difficult as an outpatient (e.g. ECT, major medication changes)
-respite for self and for other caregivers
-a comprehensive inpatient reassessment of complex or chronic problems (e.g. refractory depression or psychosis)
Many psychiatric hospital stays nowadays are brief--perhaps a few days-- with an aim to be just long enough to help someone through an immediate crisis, while quickly ensuring that there is some kind of follow-up outside the hospital.
Other stays average 2 weeks, allowing for a more thorough evaluation and change in treatments.
Sometimes there are longer stay hospitalizations, which can last for months. Manic states often require longer stays of this type.
There are chronic psychiatric hospitals for those who have severe, active, long-lasting illness and who cannot manage outside the hospital. In general, chronic psychiatric hospitalization is becoming much more uncommon, partly due to a philosophy of trying to optimize outpatient help and community resources, but partly due to budget cutting. It may be that some persons who may benefit from chronic inpatient care, and who are not doing well with other community resources, may be at risk of "falling through the cracks" in the system, and may end up struggling with a very poor quality of life, often in a homeless state.