Hi There I Have Been Using Meth For About 6months

hi there
i have been using meth for about 6months now.
and i would like to know why do i not need to take my daily dosage of my depressants?
i suffer from manic depression and am currently on 20mg citalopram.
before i started smoking i would go a few days without taking them and then i would get a aweful "withdrawl" affect. but while smoking meth i dont get that feeling at all. i do not smoke on a regular occasion but mostly over weekends.