A 13-year-old boy has developed concentration problems in school, accompanied by a significant decline in grades. When evaluated, he explains that he has been worrying about his grandfather, with whom he is extremely close. His grandfather was recently diagnosed with Alzheimer's disease, and the boy has been helping his mother take care of him. As his grades decline, he becomes increasingly sad and his energy level drops, which further hinders his ability to pay attention in school. He also complains of being restless and unable to sleep. What is the most likely diagnosis?

Choice A reason: ADHD typically presents with persistent symptoms of inattention, hyperactivity, and impulsivity across multiple settings. This patient’s symptoms are situational and associated with a recent stressor, making ADHD less likely. Choice B reason: This is the correct answer. Adjustment disorder with mixed anxiety and mood occurs when an individual develops emotional or behavioral symptoms in response to a stressor, such as a family illness. The boy’s worry about his grandfather, sadness, restlessness, sleep disturbance, and decline in school performance fit this diagnosis. Choice C reason: Separation anxiety disorder involves excessive fear or anxiety concerning separation from attachment figures, usually in younger children. While the boy is concerned about his grandfather, the anxiety is not centered on separation from a caregiver, making this diagnosis less fitting. Choice D reason: Generalized anxiety disorder involves chronic, excessive worry across multiple domains for at least six months. This patient’s anxiety is linked to a specific stressor over a short period, so GAD criteria are not met.