It is impossible for your healthcare provider to know whether you will develop insomnia while taking Effexor. Also, in some cases, if a person does develop insomnia, it is challenging to know whether these problems are because of his or her condition or Effexor itself. This is because insomnia is common with depression.
If you are taking Effexor and insomnia occurs, make sure to talk with your healthcare provider. There are other treatments that he or she may be able to recommend, including adjusting the Effexor dosage or trying another depression medicine.