A 45-Year-Old Man Comes to the Office Due to Chronic

A 45-year-old man comes to the office due to chronic insomnia.  The patient has trouble sleeping because he claims he must remain alert to protect himself from workers at a nearby chemical plant.  He says they are poisoning him by secretly dumping toxic waste in his backyard at night.  The patient's wife says, "He's been like this for the past 10 years.  He gets very upset when asked for proof, so he's going to install cameras next week."  She has never seen any unusual activity in the backyard and says that her husband has never received an actual threat or endured actual harm.  He has ordered numerous soil toxicity tests over the years, all of which have been negative.  The patient started working as a taxi driver at age 21 and continues to work for the same company.  He has no history of psychiatric treatment.  Which of the following is the most likely diagnosis for this patient?

A) Delusional disorder
B) Major depressive disorder with psychotic features
C) Paranoid personality disorder
D) Schizophrenia
E) Schizophreniform disorder
F) Schizotypal personality disorder