"I've been struggling with substance abuse since I was 16 years old," Chet wrote in a caption alongside the clip. "Finally at the age of 24 I decided to get some help.
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Chet Hanks pictured with his father Tom Hanks
"With 50 days of sobriety under my belt, I can honestly say I'm the happiest I've ever been. I'm thankful for my family and everyone who cares about me, including my fans.
"I've been blessed with the programs of AA and NA which allow me to rise above this disease. I'm learning to accept my faults and be ok with being human. If anybody that sees this struggles with addiction, feel free to reach out. Thank you for all the love and support. God is real!!!"
In the video, Chet – real name Chester – explained that he wanted followers to hear the news directly from him.
Chet Hanks made the announcement in a video posted on his Instagram page
"I have an announcement," he says on camera. "A tabloid is about to run a piece on me being in rehab for cocaine addiction. It's true and I'm currently 50 days clean and sober from everything – including alcohol."
Chet – who raps under the stage name Chet Haze – is one of four children raised by Oscar-winner Tom, who also has an 18-year-old son Truman with wife Rita.
Tom is also a father to fellow actor Colin Hanks, 37, and 32-year-old daughter Elizabeth from his marriage to Samantha Lewes.