A 15-year-old boy is brought by his father to the psychiatric mental health nurse practitioner (PMHNP) for evaluation of what he considers unusual behavior. The boy's father states that for the past 2 months, his son claims he can communicate with "aliens from another planet." During this same time, he has been withdrawn from friends and activities, and he has been less talkative at home, making it difficult to communicate with him. What is the most likely diagnosis?