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: Attention deficit hyperactivity disorder (ADHD) is characterized by persistent patterns of inattention, hyperactivity, and impulsivity that are present across multiple settings and have existed since childhood. This patient’s symptoms are acute and situational, triggered by a recent stressor (grandfather’s illness), which makes ADHD less likely as the primary diagnosis. Choice B reason: Adjustment disorder with mixed anxiety and mood is a stress-response syndrome that arises within three months of an identifiable stressor. The patient’s concentration problems, sadness, decreased energy, restlessness, and sleep difficulties are all temporally linked to the stressor of caring for a sick grandparent. This diagnosis fits the acute onset of emotional and behavioral changes in response to a significant life event. Choice C reason: Separation anxiety disorder involves excessive fear or anxiety concerning separation from attachment figures. While the patient has concern for his grandfather, his anxiety is not rooted in separation from a primary attachment figure but rather in worry about the grandfather’s illness and responsibilities at home. Choice D reason: Generalized anxiety disorder is characterized by excessive, uncontrollable worry about multiple areas of life for at least six months. The patient’s anxiety is specific to a recent stressor rather than pervasive across multiple domains, making GAD less likely.