katieb is quite right - the drugs company list every potential side effect apart from fire flood and famine, so that if any arise, they are covered against legal redress.
I have taken citalopram daily for the last ten years or so, and they suit me very well.
With any antidepressant, you will experience side-effects as they become absorbed in your system, so for a couple, maybe three weeks, you may have nausea, headaches, and some sleep disturbance, but these will all disappear as your body gets used to the new dosage.
The good news is, antidepressants are fare mor sophisticated these days than the chemical cosh drugs used years ago - and they can be prescribed to suit the needs of individual patients.
Once you are on a level, you will be fine, but asadvised, if they don't suit, then return to your GP.