most antidepressants take about 4-6 weeks to get full results since it takes that long to circulate thru your brain fully...It depends on the person as to if it will be 4 weeks versus 6 weeks since everybody's brain is different.
Normally it takes 3-6 weeks to feel the full effects. The variation is because each person's brain reacts differently to SSRI's. The chemical reactions begin almost immediately, but for relief of symptoms it takes the 3-6 weeks.