Why do some people suffer after being on a ssri like celexa (citalopram) 20mg for 6months and then off it for 2 months and have the shocks, tremors, nauseous?

Discontinuation ....: ..Syndrome.... If you stop an ssri too abruptly, you may have the symptoms that you describe above, the hallmark seems to be brief moments of light-headedness upon turning one's head quickly, together with a constant feeling of nausea. This happens more with the meds with the shorter half-lives, like Paxil and effexor, (venlafaxine) but can happen with any one of them when they have left your system.