I suppose it is possible. Rarely antibiotics have psychiatric side effects. Generally these are negative though: depression, anxiety, mania, or dissociation. Since the actual mechanism that causes these side effects isn't known nothing can be completely ruled out. It is also a possible interaction between antibiotics and other supplements or medications you are taking.
Well they kill the bad bacteria in your system. I would imagine that this can make you feel better all around making you happy
Better means happier
