A 22-year-old man reports that he hears someone knocking on his door at night, but every time he answers the door, no one is there. He thinks he hears his neighbors outside talking, even when he knows they are not home. He says he knows it’s his “imagination," but he feels “compelled” to answer the door, “no matter what time of day,” even if he is sleeping. He says he has had similar episodes “in the past,” but this has been going on for at least 6 months, and it has become problematic. What is the most appropriate diagnosis?

Choice A reason: This is correct. The patient demonstrates both obsessions and compulsions. Obsessions are intrusive, unwanted thoughts or images, such as hearing knocking or voices that are not real. Compulsions are repetitive behaviors performed to reduce distress or prevent a feared outcome, demonstrated by the patient feeling compelled to check the door repeatedly. The symptoms have persisted for over six months and cause significant impairment, meeting diagnostic criteria for OCD. Choice B reason: Schizophrenia involves persistent psychotic symptoms, such as hallucinations, delusions, disorganized speech, or negative symptoms, typically accompanied by functional decline. This patient recognizes the hallucinations as his imagination, which is inconsistent with schizophrenia. Choice C reason: Social anxiety disorder is characterized by fear or anxiety in social situations due to concern about being judged or embarrassed. The patient's behaviors are not motivated by social evaluation and thus do not align with social anxiety disorder. Choice D reason: Delusional disorder involves fixed, false beliefs that are not amenable to reason. The patient acknowledges that the experiences are imagined, which does not meet criteria for delusional disorder.