Recognition and Differential Diagnosis of Psychosis in Primary Care.

Psychosis is a symptom complex that may include hallucinations, delusions, disorders of thought, and disorganized speech or behavior. Acute psychosis is primary if it is symptomatic of a psychiatric disorder, or secondary if caused by a specific medical condition. Patients with primary psychiatric disorders are likely to have auditory hallucinations, prominent cognitive disorders, and complicated delusions. If psychosis is caused by a medical condition, the patient may exhibit cognitive changes and abnormal vital signs, and may have visual hallucinations. Illicit drug use is the most common medical cause of acute psychosis. Clinicians should ask about recent head injury or trauma, seizures, cerebrovascular disease, or new or worsening headaches. A subacute onset of psychosis should raise suspicion for an oncologic cause. Collateral history from family members is helpful in establishing the presentation and course of the illness. The physical examination should include complete neurologic and mental status assessments. Tachycardia or severe hypertension may indicate drug toxicity or thyrotoxicosis; fever may suggest encephalitis or porphyria. Suggested initial laboratory tests include a complete blood count, metabolic profile, thyroid function tests, urine toxicology, and measurement of parathyroid hormone, calcium, vitamin B12, folate, and niacin. Testing for human immunodeficiency virus infection and syphilis should also be considered. Prompt recognition of the etiology of psychosis may improve treatment, consultation, and prognosis.