I have been on 75mg of Effexor for many years . I have 'reactive depression' which means that I get into a depressive state when things happen to me, but am generally not a depressive person. When I am going through a good patch I go down to 37.5 which is apparently a low dosage and does help my general anxiety to stay on an even keel. When things get bad (for example problems at work, when my husband passed away, money worries etc) I go back up to 75mg with my doctors help and I am fine. But a couple of weeks ago I was very depressed and my doctor prescribed the usual 75mgs and I found that I could not sleep, which has never happened before . I was staying awake for most of the night, or sleeping and then waking at 1 hour intervals and I was exhausted. I am now trying to get back down to 37.5 but am having terrible nightmares. Why has this suddenly started to happen when I have been increasing and decreasing the dosage successfully for about 20 years now?