(from 2002, but still relevant today) http://www.alternativementalhealth.com/articles/diamond.htm This is quite long - probably too long for many people. Anyway, I found it interesting. It talks about studies that found various (non-small) percentages of psychiatric patients had missed medical diagnoses. It talks about general issues to be conscious of. It goes through Psychosis- Patients that Appear Out of Touch with Reality Anxiety Depression And lists symptoms to look out for that suggest a physical diagnosis, specific conditions and drugs that can cause such conditions/symptoms.