After a few years of problems with generalized anxiety, I felt fine almost immediately after I began treating mild sleep apnea. My symptoms had included anxiety, rapid heart rate and difficulty exercising due to fast heart. I found both cognative behavior therapy (more so than Lexapro) and modest exercise to be very helpful. Deconditioning really exagerates the labile cardiac and blood pressure symptons that contributed to anxiety.
But the dramatic change came with use of the CPAP machine. Treating sleep apnea has allowed me to resume normal REM sleep cycles, and after only a couple nights I found my anxiety symptoms had virtually disappeared, and I was able to exercise with a much more slowly increasing heart rate. I also have long interesting dreams, while before I woke up as soon as a vivid dream began. I've read that REM sleep is related to the brain's normal processing of anxiety.
I just wanted to share this good experience, because I spent several years worrying about my health and trying various things to releave anxiety symptoms. I'm sure there are many causes to anxiety, but sleep apnea is something to ask your doctor about. So my conclusions for myself at least were:
1. Don't sit around and get deconditioned, go for a 15 - 30 minute walk every day.
2. Try talking to an experienced cognative behavioral therapist instead of just the pill-pusher types.
3. Check if you have sleep apnea and do the treatment with CPAP machine if diagnosed.