This theory would be interesting to test.

I wonder if allergy shots would have a difference.

I’ve taken all three and never experienced depression.
I get hair crawl, jitters and troubles sleeping but never depression.

Zyrtec makes me tired. But is the best at relieving my allergy symptoms.
Allegra doesn't work for me.

Claritin on the other hand does some funky stuff to me. Makes me very light headed and has led to panic attacks. Different medications effect each person differently.

i have talking Allegra for years with no problem.

I take flonase everyday . if not I get an annoying cough and itchy throat.I sneeze everyday some days are terrible. Get swollen glands. I can deal with it all cept the cough that shit sucks. Flonase is king lol4R They gave me claritin as well I never took it though. I live in a place where allergies are terrible. I don't think the flonase does anything to me. A little sleepy maybe.