I knew an afghan war vet who couldn't speak. He hid in the corner of his room after he came home. Guy was in his 50's. Had an adult daughter he couldn't communicate with. She put him in a psychiatric hospital and he did the same shit, sat in the corner of his room, and what he told me was, the doctors said to him: "you don't have to move or do anything, you just need to know that your reaction is normal. Lots of other people react this way too."
They just kept that up until he was annoyed with them. Eventually they got him eating right and on some meds. Took him over a year but these people were professionals.
Eventually he started reacting to them more strongly, mostly getting mad at them, but, they got him talking.
Long story short, I was there the day they discharged him, and I saw him hug his daughter and they both cried.
You gonna tell me shrinks don't do anything after I've seen all that? Gtfo. You gonna tell me that guy should have silently bared his pain, in the fucking corner, barely eating? Once again, gtfo.
For the record, I was at that place too, that's how I knew him, dealing with my own shit. And what he told me was "it can work, if you let it."
I let it and I'm doing better too.