Matt's parents are devastated to have just found out that their son has been experiencing hallucinations. They immediately decide to take him to the hospital where he can be evaluated by a psychiatrist. During that time, Matt reveals that he thinks his parents are trying to poison him. The psychiatrist also notes additional disturbed thinking and social withdrawal, but no depressed mood. Which of the following psychological disorders does Matt likely have? a) posttraumatic stress disorder b) borderline personality disorder c) generalized anxiety disorder d) schizophrenia