Good advice about. You may also get some help from your community's social services organization - I don't have any personal experience here, but I believe you can get "free" help from some and they may be willing to consult with you directly, and your son if he is willing.
Depression is real, and can be dangerous, I fully support the advice of "ticked" above.
Does he see someone besides a GP for his Mental disorders? Therapists? He should be seeing someone like that to make sure the meds are working properly and if they are not they need to be changed.
If he is suicidal then I think you can have him brought to the hospital because he is at risk at harming himself. That is if you are desperate of course and can't get to him to see a therapist. At the age of 22 its hard because it really is his choice.
Is he compliant about getting better and seeing someone about his suicidal thoughts?
Does he have any jaw issues, or does he read a lot about things online to do with his health?
My sister is schizophrenic and when she is having a psychosis moment she says odd things as well however hers is more religious things that come out.
The meds could be causing suicidal thoughts if he didnt have them before and they do sometimes make you feel like you are just there with no emotion happy or sad. That is the draw back unfortunately.