A 29-year-old single woman presents to the PMHNP for evaluation of a chief complaint of fatigue. She states she has been feeling "tired" and "empty" for the past 4 years. She sleeps up to 11 hours a day and is still tired. She has trouble concentrating and has difficulty making decisions. She has gained 10 pounds over the past 2 years due to overeating and little physical activity. She reports no suicidal ideation or manic symptoms, and no delusions or hallucinations. What is the most likely diagnosis?

Choice A reason: Major depressive disorder typically involves discrete episodes lasting at least 2 weeks with more acute severity. This patient’s 4-year chronic course suggests a different diagnosis. Choice B reason: Generalized anxiety disorder is characterized by excessive worry rather than chronic low mood, fatigue, and anhedonia. Choice C reason: Persistent depressive disorder (dysthymia) involves chronic depressive symptoms lasting at least 2 years in adults. The patient’s long-term low mood, fatigue, hypersomnia, poor concentration, and weight changes are consistent with dysthymia. Choice D reason: Cyclothymic disorder involves fluctuating hypomanic and depressive symptoms; this patient has no hypomanic features.