Antidepressants definitely mess with your sleep cycle. Ironically, not sleeping can make you depressed. >.<

I was on SSRI's for a number of years. Weaning off of them changes a great deal of things, but you will likely notice mood instability for a while as your brain chemistry adjusts to regulating itself again.

Make sure you're getting plenty of sunlight and try to stay active during the transition. It will help your mood stay stable during the regulation phase.

Just my two cents from experience. Not a doctor. :)