A 40-year-old man reports episodes in which he unexpectedly feels a surge of intense fear that peaks within minutes. During this time he feels dizzy, has shortness of breath, heart palpitations, and feels like he is "going crazy." These episodes seem to come "out of the blue" with no trigger that he can identify. He has had them when he has been napping on the weekend or during a break at work. He is starting to think he is really "going crazy," because he has no medical conditions, doesn't drink or smoke, and says there are no new stressors in his life that could be causing this. What is the most likely diagnosis?

Choice A reason: Panic attacks are the symptomatic episodes themselves, not the diagnosis. A diagnosis of panic disorder requires recurrent, unexpected panic attacks with persistent concern or behavioral changes related to the attacks. Choice B reason: Panic disorder involves recurrent, unexpected panic attacks with significant concern about future attacks or their implications. This patient demonstrates multiple unprovoked episodes with accompanying worry, consistent with panic disorder. Choice C reason: Generalized anxiety disorder involves chronic, excessive worry about multiple domains, often with tension and restlessness. The abrupt, episodic, intense fear seen here is characteristic of panic disorder rather than GAD. Choice D reason: Substance or medication-induced panic disorder requires evidence of exposure to a causative substance. The patient denies use of substances or medications that could trigger these episodes.