I have been on effexor xr for more tha 2 years. Before that I had been on prozac for about 8 years. I have PMS (hormonal) issues that is why they started me on prozac. Anyway, I went from 150 mg 2 months ago to 75 mg because I felt the 150mg was making me have insomnia, I noticed if forgot to take the effor I would sleep better. It has taken me a while to figure this out because I usally take my meds everyday. My question is can you develope side effects after being on effexor xr this long. I am in the proccess of going down to 37.5 mg so I can take myself off this medication.