<prompt> An old patient was brought to the hospital with the history of auditory hallucinations. He states that, some unknown peoples are conspiring against him. He hears them talking on his every actions continuously. What could be the most likely diagnosis:DementiaDelusional disordersSchizophreniaAcute psychosis  <response>: Ans. c SchizophreniaRef.: Harrison 19th ed. 2720 Hallucinatory voice commenting keeping up a running commentary on ones behavior, thought or action in the third person third person hallucination is a classical presentation of schizophrenia. The patient presented here with 3rd party auditory hallucination, which is a very characteristic finding of Schizophrenia.Diagnostic criteria for schizophrenia according to DSM-IV and ICD 10 DSM-IVICD-101 criteria for 1 month Bizzare delusions Hallucinations consist of: Hallucinatory voice commenting keeping up a running commentary on ones behavior, thought or action in the third person third person hallucination Voices discussing or arguing i.e. hallucinations of two or more voices discussing or conversing with each other Thought echo insertion withdrawal broadcasting Delusion of control Hallucinatory voices Persistent delusionsOr 2 Criteria Delusions Hallucinations Negative symptoms i.e. affective flattening, alogia or avolition Grossly disorganized or catatonic behavior Disorganized speech eg frequent incoherence or derailment Thought block disorder Persistent hallucinations Negative symptoms CatatoniaTime course Symptom for 1 month 6 months social occupational disturbance 1 month most of the timeExclusions Brief mood disturbance or schizoaffective disorder Direct effect of drug abuse medication medical condition Schizoaffective disorder or extensive depressive manic symptoms Drug intoxication withdrawal, overt brain disease. Negative symptoms respond poor to treatment poor prognosis while positive symptoms are well responsive to treatment better prognosis.Positive SymptomsNegative Symptoms Hallucination Delusion Anhedonia: loss of interest in things which were interesting before. Avolition: lack of desire to achieve goal Alogia: poverty of speech Attention deficit Social withdrawal 