The main finding in narcoleptic patients as compared to control subjects was major changes in the 'number of arguments with partner, family, or friends. This can be interpreted as having a protective function and it suggests that psychological mechanisms are present since the beginning of the disease.Now I think we all would agree with the first part.
But the irritability is not "behaviorally protective" in any way.
These authors have clearly never tried to rebuild their life after walking out on a spouse while floridly ill...
Crankiness is one of the most damaging effects of narcolepsy.
And irritability is a primary symptom of infection, an indication of acute illness, thankyouverymuch.