John Michael Montgomery in Rehab
05/13/2008 AT 09:40 AM EDT
The "I Swear" singer, who had a string of No. 1 hits in the '90s, says his abuse troubles are due to "severe anxiety attacks and sleep disorder."
Of his rehab decision, Montgomery wrote: "I will be disappearing for a while to try and defeat the demons that have stripped me of my energy of life and good health for so many years now ... However long it may take, I'm gonna fight to the end and come out stronger."