I have been unlucky enough to be the guest of two different psychiatric hospitals. In addition, I have worked in nine psychiatric hospitals in a professional capacity. Most people, even professional psychiatrists, have a rather naive view of what happens in a mental hospital. Private psychiatrists who spend most of their time treating private patients for depression and anxiety may have very little experience with a real psychiatric hospital. Ordinary people may get their views of psychiatric hospitals from books and movies, such as the extremely optimistic "Girl, Interrupted," during which a forced psychiatric patient rediscovers her joy in life while receiving a great deal of individual therapy and developing relationships with other inmates.
The reality of the psychiatric hospital is, unfortunately, much bleaker than even popular culture would lead us to believe. The hospital is a good place for low-functioning people with thought disorders or severe personality disorders to get stabilized on their meds. The hospital is no place for a high-functioning depressive.
What could you expect if you were involuntarily hospitalized? First, don't expect for there to be people like you around. Most people involuntarily hospitalized are the aforementioned low functioning folks with thought disorders (like schizophrenia) and severe personality disorders (like borderline personality disorder). "Low functioning" means that these people will mostly have a hard time engaging in normal activities of daily living, like washing themselves, feeding themselves, and having a conversation. You will share a room with one or more of these people.
You won't get individual therapy (one-on-one talk therapy). It's too expensive, and not very effective for the hospital's normal clientele, those low functioning folks with thought disorders. The usual plan for low functioning people with thought disorders is to "stabilize them on meds" - they come in psychotic, they are given antipsychotic medication for a while, and their psychosis disappears. (Medication may be forced in most states. Some states require a hearing before forced medication may happen; these are generally rubber-stamp proceedings.) This process has a very high success rate for low functioning people with thought disorders; individual therapy is not seen as effective or necessary.
Generally, hospitals try to apply the stabilize-on-meds approach to high functioning depressives, with mixed results. As mentioned above, individual therapy is not available. Instead, expect mandatory "group therapy." Group therapy, in a private, outpatient setting, is often interesting and productive, given a group of intelligent, high-functioning, thoughtful people. You will not find that in a hospital. Instead, you will find yourself in group therapy with that same group of low functioning people with thought disorders that you've been rooming with and eating with and smoking with during your stay. Often, group therapy takes the form of practicing activities of daily living - say, writing a letter, or washing oneself. This would be very helpful for a low functioning person with a thought disorder; it is humiliating and harmful for a high functioning depressive.
You may meet with a doctor once or twice during your stay. The doctor does not want to talk to you. The doctor wants to know if you are tolerating your meds, and if you have figured out how to answer questions about your suicidal intent correctly, so that you may be released. Most suicidal high functioning depressives quickly figure this out, and answer that they feel much better, that the meds are working fine, and that they have no further suicidal ideation.
The stabilize-on-meds approach for depressed patients is especially ridiculous, given that anti-depressant medications don't work any better than placebos. Given that the hospital doesn't help the high functioning depressive, except to medicate him or her, the purpose of the hospital in this context becomes clear: it is a prison. Hospitalization doesn't help people become non-suicidal. It merely teaches the high functioning depressive to make sure he or she succeeds the next time he or she attempts suicide. And never to be honest with a doctor again about suicidal ideation.