A 16-year-old girl presents with anxiety, irritability, and feelings of sadness. She reports that she has been experiencing some difficulty with friends, is spending most of her weekends sleeping, and is struggling with low self-esteem. She has lost about 10 lb in the past several months (5 ft 3 in and 119 lb, BMI 21.1). She does not use tobacco but occasionally drinks alcohol moderately. She had an adenoidectomy at age 7 but has no other health conditions, and her mother has a history of generalized anxiety disorder. Her physical examination is unremarkable.