A key differential to consider when diagnosing Illness Anxiety Disorder is:

• A. Somatic Symptom Disorder.
• B. Generalized anxiety disorder.
• C. Schizophrenia.
• D. Major depressive disorder.

Answer: (A)

The concept being tested is how to tell Illness Anxiety Disorder apart from related conditions that also involve health concerns. The best differential is Somatic Symptom Disorder because both disorders center on concerns about bodily health, but they differ in what drives the distress.

In Somatic Symptom Disorder, there are one or more actual somatic symptoms that are distressing or disruptive, and the person spends excessive time, energy, and thinking about those symptoms. The physical symptom itself is real and central to the distress.

In Illness Anxiety Disorder, somatic symptoms are either very mild or not present at all, yet there is a preoccupation with having or acquiring a serious illness, accompanied by high health anxiety and maladaptive health-related behaviors.

So, if the presentation shows prominent somatic symptoms with disproportionate worry about them, SSD is the more fitting diagnosis. If the presentation shows little to no somatic symptoms but persistent worry about illness, IAD is more likely.

Generalized anxiety disorder involves broad worry about many domains and is not limited to health concerns. Schizophrenia would involve psychotic symptoms such as delusions or hallucinations, not just illness-related anxiety. Major depressive disorder centers on mood disturbance and anhedonia, not primarily on health-focused somatic concerns.