John Michael Montgomery has voluntarily checked himself into a rehabilitation treatment center for substance abuse, due to severe anxiety attacks and sleep disorder, his management company said Friday (May 9). Montgomery has canceled all concert dates and personal appearances for the next 30 days. After being arrested in 2006 on alcohol, drugs and weapons charges, he entered an Alford plea to the DUI charge, acknowledging there was sufficient evidence for a conviction. The other charges were dismissed as part of the plea bargain. In a statement, Montgomery said, "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. I assure you that however long it may take, I'm gonna fight to the end and come out stronger." Montgomery is scheduled to release an album on his own label in September, and he has a new single at country radio titled, "If You Ever Went Away."