I'm don't think that is necessarily true. I suffer from severe mold problems. It resently got so bad that I started to suffer from Depression and other mental issues. I was not exercising for a few days and the problem got worst. As soon as I resume my exercise all mental disturbances were gone.
I then added Niacinamide, which I take the same dosage everday. Once I take it everyday, even if I don't exercise I don't experience any mental disturbances.