Olympic gold medalist Tyler Hamilton, who was banned for two years for doping in 2005, is to retire after testing positive for a banned antidepressant.

The positive test could bring a ban of eight years for the 38-year-old rider, who is suffering from depression.

"I took a banned substance," said Hamilton. "I accept the consequences. You make mistakes in your life and I accept the penalty like a man."

He won gold at Athens in 2004 but the win was clouded by the doping scandal.

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