How long: disability. How long to receive disability on the basis of a mental disorder varies from state to state. In my california, the social sec. Or "ssi" office is seriously backed up, and my patients wait anywhere from 2 months [on the "fast" side!] to 2-5 years, once you go thru appeal process. The more evidence, old records, reports u can give ssi, the better. Schizophrenia, serious illness lesser time maybe.
Can be indefinite. Or permanent, which means once it starts, the disability can continue until the person recovers and become able to go back to work again. Lots of paperwork and review involved to get on permanent disability, but worth doing to help someone who needs it.