Brain injury forces Dragons centre to quit
According to the BBC, the 28-year-old, who has made has made 119 appearances since 2010 and scored 22 tries, says a specialist's advice led to his decision.
"A neurologist said that playing rugby wasn't an option due to two major trauma scars that I had sustained on my brain," said Hughes.
"The decision was made there and then for me."
Hughes has not featured since September 2017 and attempts at rehabilitation have been unsuccessful.
He left Dragons in 2014 for Bristol and later that year signed a two-year deal for Exeter Chiefs.
Hughes made 10 appearances for the English Premiership side before returning to Dragons in October 2015.
Dragons head coach Bernard Jackman described Hughes as "a versatile player that had brilliant pace and evasion".
"I would like to take this opportunity to thank Adam for the huge contribution he has made to the Dragons," added Jackman.
Hughes is the third Dragons player in three seasons to retire after suffering head injuries following Matthew Pewtner in 2016 and Ashley Smith in 2015.