Well there are some answers to it, allthough there isn`t one 100% clear
answer. Probably it has something to do with the increase of serotonin
causing a decrease of dopamine/norepherine in some areas of the brain. This
is why wellbutrin, an NDRI is often used to counter the sexual side effects
caused by SSRI`s (i`d definately recommend discussing this with your dr if
the sexual side effect bother you, as they can lead to problems with your
wellbeing by themselves).