anxiety
"After 2 heart surgeries I developed severe anxiety.  I also had constant chest pain that was not cardiac related as well as being afraid to sleep lying flat because I couldn't breathe.  Before that I was always the calmest person in any situation and suddenly being distracted by irrational fears was devastating for me.  My doctor prescribed Lexapro 20 mg daily which I initially did not take because I didn't want to be on an SSRI.  After a severe panic attack while on duty, I started taking the medication and experienced complete relief of my anxiety and panic attacks within a week.  I have not experienced any of the side effects except some gas, and my high sex drive has not been affected."