His manager, Brendan Rodgers, revealed on Wednesday afternoon that the Scottish international will be unavailable for an indefinite period as he seeks professional help.
Shortly after the news broke, fans of all clubs came together to offer support and encouragement to the 28-year-old.
Speaking to the Celtic website, Griffiths thanked people for their kind words and vowed to come back a “better and stronger person”.
He said: “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.
“I thank you all sincerely and want to let you know I’m doing all I can to come back as soon as possible, a better and stronger person.”