A teenage girl presents with anxiety, nightmares, and insatiable hunger. What diagnostic test is likely to provide the most useful information?

In this scenario, the symptoms of anxiety, nightmares, and insatiable hunger could suggest various underlying issues, including potential substance use disorders. A urine drug screen is the most useful diagnostic tool in this case because it can help identify whether the patient is using substances that could contribute to her symptoms. For instance, certain drugs, particularly stimulants or hallucinogens, can lead to anxiety and disturbances in sleep, while also affecting appetite.

The other diagnostic tests have specific applications but may not directly address the symptoms presented in this case. Serum TSH is primarily related to thyroid function and would not effectively evaluate the psychological or behavioral symptoms described. The Minnesota Multiphasic Personality Inventory is a psychological assessment tool more suited for diagnosing personality disorders rather than understanding acute symptoms. An electroencephalogram measures brain electrical activity and is typically used to evaluate seizure disorders, not the psychological and behavioral symptoms presented here. Thus, utilizing a urine drug screen is the most informative step towards understanding the underlying causes of the girl’s symptoms.