It absolutely plays a role in fatigue. I brought this very subject up with my Derm, Rheumy and Pain Mgmt docs and all three had similar if not exact responses. Science doesn’t yet know the full scope on this but they think it has something to do with the fact that our immune systems are in overdrive. Throw in systemic inflammation and the body fights to accommodate that. In addition, dealing with physical and emotional pain plays another part. Throw this all together and we have the perfect conditions for bringing on fatigue!
Finally, another aspect of fatigue and P and PsA could be cardiac. There is mounting evidence that those of us that deal with P and PsA have a significantly higher chance of experience heart disease. Speaking from experience, in May 2016 I suffered what is known as a STEMI (ST Elevated Myocardial Infarct) aka Widow Maker Heart Attack. Wouldn’t wish that on the evilest of evil...but what I experienced beforehand was FATIGUE! I mean absolute no energy need 3 naps a day and still wasn’t enough fatigue. If this is you please go see your doctor!