"i&#039;ve been on 40mg for almost 8 weeks now.  was working great in the beginning, especially weeks 3-5, but for some reason the beneficial mood effects wore off and i don&#039;t feel any different now than before.  the only thing i can think of is around that same time i started seeing a shrink and he put me on xanax xr 0.5mg 1-2 times per day.  could the xanax xr have killed off the positive effects i was having with the viibryd?  not sure yet. by the way, i had literally no negative side effects from taking this medication.  i always take it in the morning, never at night.  tried that once and it kept me up all night."