1. Safety!
2. Rest!
3. Medication management/titration can be handled much faster with 24/7 supervision and daily visits with doctors. Sleep regulation and getting a handle on severe depression, anxiety, psychosis, etc. are priorities for med management generally.
4. Therapy/skills/education groups -- sometimes individual
5. Intervention/assistance through social workers to set up services, therapists, pdocs etc. once discharged.
6. Detox is often part of the plan as many psych patients are also dealing with issues with substance abuse.
7. ECT, by the way, is only started (generally) inpatient, but moves to being an outpatient treatment fairly quickly.