There are extreme side effects of going off effexor cold turkey and it can be very harmful. You must go off the drug slowly and you will not have experience the crazy withdrawl symptoms.. It would be helpful to first cut the dose in half or by 1/3 for 2-4 weeks then cut again for the next 2-4 weeks until you are off of the drug. Normal side effects of going off of the Effexor cold turkey are severe head aches, not being able to concentrate, an uneasy feeling in your head, mentally unstable, increased appetite, tremors, ..etc