A patient is brought with 6 month history of odd behaviour. There is a history of a family member having disappeared some years back. He seems to be talking to himself and sometimes muttering to himself loudly. The likely diagnosis is -

This patient is having:- Disorganized behavior & thinking (talking to himself) Disorganized speech (muttering to himself loudly) Symptoms for 6 months Diagnostic criteria for schizophrenia:- 2 or more of the following features (each present for more than 1 month), causing social or occupational dysfunction for more than 6 months:- 1)    Hallucinations; 2) Delusions; 3) Disorganized speech; 4) Disorganized or catatonic behavior; and 5) Negative symptoms.