"As Joe has alluded to in interviews over the past year, he has struggled with the issue of substance abuse," said a statement from Lytle Management. "In order to become a healthier person and deal with long-standing issues, he has entered into a rehabilitation program for consultation and treatment."
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The statement was posted on the country singer's Web site.
His publicist, Jennifer Bohler, confirmed the statement, but wouldn't comment further, according to The Tennessean newspaper. A message left at Lytle Management's office late Friday night wasn't immediately returned.
It wasn't clear when Nichols, 30, entered the program.
His album "Real Things" was released by Universal South Records LLC earlier this year.