Leigh Griffiths hopes to return "a better and stronger person" after Celtic gave the striker time off to deal with his personal problems.
Celtic boss Brendan Rodgers said on Wednesday that Griffiths, 28, would be "out of football" while he gets help with "ongoing issues", including some relating to his mental health.
"I just wanted to thank everyone at the club and so many Celtic fans and other people who have sent me such kind and powerful messages of support," the Scotland international said.
He added that: "I'm doing all I can to come back as soon as possible a better and stronger person."
Griffiths has struggled to hold down a regular place during a season disrupted by injuries and has scored six times in 22 appearances.
Rodgers declined to elaborate on the striker's issues but said they had been ongoing for "a number of months".
Griffiths withdrew from the Scotland squad to face Israel and Portugal in October to focus on his fitness.