A 23 year old engineering student is brought by his family to the hospital with a history of gradual onset of suspiciousness, muttering and smiling without clear reason, decreased socialization, violent outbursts, and lack of interest in studies for 8 months. Mental status examination revealed a blunt affect, thought broadcast, a relatively preserved cognition, impaired judgment and insight. He is most likely to be suffering from -
This patient has:-


Delusions of control (thought broad casting)
Disorganized speech (muttering)
Disorganized behavior (smiling without clear reason, violent outbursts)
Negative symptoms (blunted affect, lack of interest, decreased socialization).
Duration of 8 months


Diagnostic criteria for schizophrenia:- Two or more of the following symptoms (each should be present for 1 month or more) and causing social or occupational dysfunction for 6 months or more.


Delusion  
Hallucinations
   Disorganized speech
Disorganized or catatonic behavior
Negative symptoms                                                                                                                                                                      
Only one of the above is required if delusions are bizarre or there are third person hallucinations.
Delusional disorder
Depression
Schizophrenia
Anxiety disorder