Illness Anxiety Disorder (Hypochondriasis)

Illness anxiety disorder (formerly hypochondriasis in DSM-IV) is a psychiatric condition defined by persistent preoccupation with having or developing a serious illness — crucially, in the absence of significant somatic symptoms, and USMLE Step 1 tests it almost entirely through its contrast with somatic symptom disorder. Students who learn this superficially often picture someone with lots of unexplained physical complaints, but that's somatic symptom disorder. Illness anxiety disorder is about fear and preoccupation, not symptoms themselves. Step 1 tests whether you can make that distinction cleanly.

The exam typically presents a vignette where a patient has had extensive negative workups, returns repeatedly for reassurance, and remains convinced something is seriously wrong — despite minimal or no actual physical symptoms. The key clinical feature is that reassurance doesn't work: a patient leaves the doctor's office feeling briefly better, then the preoccupation returns. Step 1 tests this in two main ways: pure recall of the diagnostic criteria, and differential diagnosis questions where you must distinguish illness anxiety disorder from somatic symptom disorder based on what's driving the clinical picture.

The trickiest part is the differential axis. Both disorders involve medical-seeking behavior and distress, so students conflate them. But the distinguishing question is simple: Is the patient distressed because of physical symptoms they're experiencing, or because they're afraid of having a disease despite feeling okay? If it's the latter, that's illness anxiety disorder. Also worth knowing: the DSM-5 rename from 'hypochondriasis' to 'illness anxiety disorder' trips up students who study from older materials — on USMLE Step 1, these terms are functionally equivalent.