A 23-year-old man is brought to the physician by his family due to concerns about his behavior. The patient’s parent tells the physician that for the past month, the patient has been telling them that he is receiving signals on the television from a secret organization to “save the world from the upcoming alien invasion.” His parent adds that they sometimes see the patient communicating
with people who are not there. The patient dropped out of his college courses seven months ago after his grades deteriorated, although he was an excellent student before. At that time, the patient also stopped taking care of his hygiene, often not showering for multiple days, and he has withdrawn from his friends and family. Past medical history is noncontributory, and the patient does not drink alcohol
or use recreational drugs. Which of the following is the most likely diagnosis?