A 20-year-old with one year of auditory hallucinations and bizarre behavior; labs are normal; hyperreflexia and mild resting tremor; Utox is negative. What is the most likely diagnosis?

• A. Schizophrenia
• B. Bipolar disorder
• C. Substance-induced psychosis
• D. Delusional disorder

Answer: (D)

When psychosis has persisted for a significant time but the person’s overall functioning remains relatively intact and there isn’t a clear pattern of disorganized thinking, negative symptoms, or widespread mood disturbance, delusional disorder becomes the leading consideration. In this scenario, the patient has a year-long history of auditory experiences and odd behavior, yet there’s no description of marked disorganization, flattened affect, or substantial functional decline, and laboratory and toxicology data are unrevealing. Such a profile fits with delusional disorder, where fixed delusions can be present for a long period without the broad spectrum of schizophrenia symptoms. The mild motor findings (hyperreflexia and resting tremor) could reflect unrelated or medication-related extrapyramidal effects rather than defining a primary psychotic illness.