[Verified Answer]: A 27 yr. old man presents in the ER, escorted

A 27 yr. old man presents in the ER, escorted by PD for an evaluation “for causing a ruckus outside a grocery store and threatening store customers.” The patient refuses to participate much during an interview. He yells “let me go or they are going to get me! They have been after me for years! You can’t let them get me!” He denies depressed mood or SI/HI or A/V H, and prior psychiatric and medical problems. He denies taking Rx meds or illegal drugs. He ends the interview stating “they can hear us”. On mental status examination the patient appears disheveled and dirty, he acts suspicious and guarded, avoiding eye contact. His speech is difficult to follow, affect is blunted. He appears to be responding to internal stimuli. What conditions need to be ruled out before a psychiatric diagnosis can be made? What is the diagnostic work up? Does the patient require psychiatric hospitalization? What is the most likely diagnosis and the evidence to support this?