It is impossible for your healthcare provider to know whether you will develop insomnia while taking Effexor XR. Also, if insomnia does occur during treatment with Effexor XR, it is difficult to know whether the insomnia is actually caused by the condition or Effexor XR itself. This is because insomnia is common with many of the conditions that Effexor treats. For example, a number of people with depression report insomnia.
If you are taking Effexor XR and insomnia becomes a problem, 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 XR dosage or trying another anxiety or depression medicine.