Hull have released scrum half Brett Seymour from his contract.
The 28-year-old Australian has been on compassionate leave since being involved in a traffic accident in Hessle in March.
"I wish to thank all the FC fans for their ongoing support," Seymour told the club's official website. "I have never experienced such passionate, supportive people and we are forever grateful.
"Our daughter Monroe Maria was born in Hull so this city will always hold a very special place in our hearts.
"I now focus 100 per cent on getting well. Thank you for everything."
Hull's director of rugby, Shaun McRae, told the club's official website: "Brett is at a stage where he needs to be concentrating on a number of important aspects of his life, other than rugby league.
"He leaves Hull FC with our best wishes for the future."
Last month, it was revealed that Seymour had booked into the Sporting Chance clinic to tackle depression.
Seymour has previously been sacked by two Australian clubs, Brisbane Broncos and Cronulla Sharks, for alcohol-related incidents.
He was also banned from driving for seven months by New Zealand police after being convicted of drink-driving and failing to stop for police in November 2011.