Hamilton says he's retiring from cycling

American cyclist Tyler Hamilton announced his retirement Friday after testing positive for the steroid DHEA, which he said he knowingly ingested in an over-the-counter herbal antidepressant.

It was the second doping offense for the veteran rider, who tested positive for homologous blood transfusion in 2004 and served a mandatory two-year suspension even as he disputed the test results through two rounds of arbitration.

Hamilton likely would face a suspension of eight years to life for his second offense.

Hamilton, 38, said he decided to admit to the violation in order to concentrate on an ongoing battle with clinical depression that was first diagnosed in 2003.

At the time he bought the supplement, which is marketed under the brand name Mitamins Advanced Formula for Depression, Hamilton was in a "desperate" emotional state triggered when he went off his prescription medication cold turkey, he said. DHEA is clearly listed among the over-the-counter drug's ingredients.

"Right now, I need to deal with my own issues and take care of myself," he told ESPN.com from his home in Boulder, Colo., before holding a media teleconference Friday. "Did I take it knowing it was on the banned list? Yes. Did I take it because it was performance-enhancing? Absolutely not."

He added that he regrets any negative impact the events may have on the sport, and feels he has let down his Rock Racing teammates and owner Michael Ball, who offered him a job in late 2007 when Hamilton was considering quitting the sport.

Ball said he trusts Hamilton's account and supports his decision, albeit with mixed emotions.

"For him to have to retire on this note is a very tough pill to swallow," Ball said. "Obviously, my personality is to fight, but that won't help Tyler. This is much bigger than a bicycle race -- this is a man coming to grips with an illness."

One of the best-known and most accomplished American cyclists of his generation, Hamilton spent the first half of his professional career with the U.S. Postal Service team and became one of Lance Armstrong's most valuable support riders. Hamilton went on to lead two different European teams, CSC and Phonak, but his reputation began to unravel in 2004 shortly after he won the Olympic gold medal in the time-trial event.

A month later, an anti-doping test at the Tour of Spain revealed the presence of another person's blood in his system.

Hamilton's unsuccessful defense attacked the science behind the test and offered a number of alternate explanations for the result, but his credibility suffered in the process -- a situation that was exacerbated by documents that later surfaced linking him with a major doping investigation in Spain.

He denied any involvement, and like many names floated in the Operacion Puerto scandal, Hamilton was never charged or cleared.

Hamilton said he knows his explanation of his recent positive test will be met with skepticism in many quarters.

"There's always going to be doubters," Hamilton said. "I understand I'm going to have a few more doubters now."

He said he stands by previous assertions that he did not previously use performance-enhancing drugs or illicit blood-boosting techniques.

A case against Hamilton will proceed despite the fact he is retiring from competition. As outlined under the U.S. Anti-Doping Agency's protocol, a panel of scientific and legal consultants reviews the evidence to decide whether the agency should pursue a case and if so, what sanction to recommend. The accused athlete then has 10 days to decide whether he wants to contest his case in arbitration.

A lengthy suspension would be moot in competitive terms since he does not intend to race again, but it could affect his ability to come back to cycling in another capacity and further impact his image. He could try to present mitigating circumstances to reduce the sanction.

"We'd like to work out a resolution that complies with the rules but also takes Tyler's circumstances into account," said Chris Manderson, Hamilton's Irvine, Calif.-based attorney.

Hamilton said the events that led up to his positive test in early February began in late 2003 when a Boston physician diagnosed him with clinical depression. The Marblehead, Mass., native had just enjoyed the most successful season of his career, finishing fourth in the Tour de France.

"From the outside, my life was going great, but on the inside I was going to pieces," he said.

Depression runs in Hamilton's family and has affected his mother and his maternal grandmother, who committed suicide. His older sister, Jennifer Linehan, who also said she suffers from the illness, said she felt her brother might be susceptible some time before he sought treatment.

"I couldn't fix it for him," she said in a telephone interview. "He needed to be able to fix it himself."

Hamilton said he kept his condition a secret from all but family and a few close friends.

"I wanted to be a leader, and I didn't want to show signs of weakness," Hamilton said. "It's a sign of failure, and athletes are afraid to fail. I've always been afraid to fail."

Dr. Paul Berger of the Boulder Holistic Medical Center confirmed that he has prescribed medication and treated Hamilton for depression, anxiety and sleep disorders for the past two years.

The cyclist took the prescription antidepressant Celexa for several years and found it was effective. But 2008 proved an especially challenging year personally as he split with his wife of nine years, and his mother, Lorna, was diagnosed with breast cancer.

Hamilton said he doubled his dose of antidepressants and found himself struggling with the side effects. He then decided to stop taking the medication altogether -- "a big, big mistake, something I might never forgive myself for," he said.

Hamilton trained erratically last winter, much of which he spent in the Boston area to be with his ailing mother, and arrived at Rock's Southern California training camp in early February out of shape and very much out of sorts.

"I obviously wasn't thinking clearly," he said of his decision to buy the Mitamins supplement. "Looking back, I wasn't in the right mental state to even be there."

Hamilton said he took the supplement for two days before he was targeted for a surprise out-of-competition urine test at the team hotel on Feb. 9.

Even then, Hamilton said he wasn't terribly worried he would test positive because he thought the concentration of DHEA would be low. (Tests conducted during the Tour of California -- where Hamilton finished second-to-last of the 84 men who completed the race -- were negative, a fact confirmed by race organizers.)

"But whether it showed up positive or not, it was wrong, and I should pay the consequences," Hamilton said.

The B, or backup, sample confirmed the first result.

DHEA is produced naturally in the body by the adrenal gland and eventually can be converted into other hormones including androstenedione, testosterone and estrogen. Claims about DHEA's effectiveness as a muscle-builder, fat-burner and anti-aging tonic -- and its potential to treat numerous other conditions, including depression -- are a subject of debate. It is a scourge for those concerned about doping in youth sports, as it is readily available in over-the-counter supplements and online.

Bonnie D. Ford covers tennis and Olympic sports for ESPN.com.