What are some of your favorite tips and tricks for teasing that apart?
I’ll start: with anxiety there’s a predominance of perseveration and cycling through the same set of themes that patient is anxious about.
Wouldn't the typical cognitions accompanying the two states be somewhat distinct with anxiety always involving a fear of some sort that--at some level--the patient should be able to articulate or that their behavioral patterns (escape, avoidance) would make reasonably clear?
It always bugs me when people report 'anxiety' (or others report 'anxiety' on their behalf) but there is no actual fear, worry, or apprehension involved nor is there clear behavioral inclination to avoid/escape or avoidant or escape behavior. Anxiety is a motivational state and not all anxiety is about the same thing. The 'anxiety' in panic disorder, per se, is catastrophic misinterpretations of bodily sensations fearing that they portend some horrific medical problem (e.g., that the patient is having a heart attack or going insane). Generalized anxiety disorder is more like chronic arousal due to multiple day-to-day worries (about bills, their family's mental health, etc.).
Sometimes sympathetic nervous system hyper-arousal is just...sympathetic nervous system hyperarousal (for whatever reason) and not actually 'anxiety.'
Also, isn't the emotional valence of hypomania generally positive whereas the emotional valence of actual clinical anxiety negative. One leads to relatively productive goal-directed behaviors whereas the other is generally unproductive and wouldn't be part of a goal-directed (other than escape/avoid) enterprise. Another way of saying it is that hypomania as an emotional state would probably involve an impulse to 'approach' certain things/outcomes whereas the emotional state of anxiety would be more characterized by an impulse to escape/avoid something. They certainly would feel different to the patient. How does the patient describe their emotional state to you? How do you 'feel' in the room with them?
Finally, depending on your practice environment, the relative base rates of presentations involving 'anxiety' vs. [true] hypomania would be expected to differ markedly with anxiety presentations, on average, being far more prevalent (especially in outpatient settings but even in inpatient settings).
Edit: I apologize, I just now realized you stipulated something you call 'irritable hypomania' in your original post. I wasn't aware that there was such a thing. My understanding (which may be outdated) was that often full-blown mania proceeds into the territory of irritability/dysphoria. I wasn't aware that this was a characteristic of hypomania. From a quick Google search I see that the field has developed a more 'nuanced' understanding of the concept of hypomania to include dysphoria (but...this is distinct from the concept of a 'mixed' episode?).