Yep, I almost never drink coffee more than 3 days in a row because it loses its affect. Luckily, intolerance comes back after only a day or two off.
Did it affect you? Yes, it had an effect.
The psych study showed the meds were effective in improving patents' affect (mood).
I want to effect (bring about) change by doing X.
HTH!
Effect duration for a psychoactive is related to half-life, but they aren't identical, and 'reset time' varies widely, e.g. MDMA is over in about 4 hours but it takes at minimum of two weeks before one can get a comparable effect again.