Is it possible that problems like, hearing voices and visualisations can be caused by some form of depression?
Probably not depression, though the long term stuff he’s been through could be causing it by virtue of mental trauma. It’s not very likely though. The symptoms sound more like schizophrenia. First, get him tested for food intolerance as about half of all cases of schizophrenia are caused by diet. Dietary intolerance would also account for low energy which would make him appear to be depressed. If it doesn’t produce a result then he will need to talk to a doctor.