Hamilton, the current US national road racing champion, and disputed 2004 Olympic gold medalist in the time trial, says he is leaving professional cycling to deal with his own clinical depression.

He was first diagnosed with depression in 2003, and has been battling the condition ever since.

Hamilton will also reveal that he tested positive for the banned steroid DHEA in an our-of-competition test on February 9th of this year. He claims that the failed test was the result of an over-the-counter medication that he was taking to treat his depression. That medication contained DHEA, which showed up in small quantities in his test.

Hamilton, age 38, has served two previous suspensions from the sport, the first for blood doping that banned him from competition from September 2004 until September 2006. A second suspension, for his involvement in the "Operation Puerto" scandal, kept him out of the sport until the spring of 2007.