Dude, same thing here. I do 130-150 BPM for 45 minutes. Immediately post-workout I feel pretty damn good. But for the next few days or even weeks I just regress significantly...dull pain in the lower skull, brain fog and general malaise.

It sucks because the exercise definitely helps my anxiety, however the regression of symptoms just leads to further anxiety and depression.

I've been going consistently for 2 months now...hoping I can overcome the threshold.