Just as each achievement by one of the Kennedy clan adds luster to what be may the closest thing to American royalty, so each misstep is dissected in the public eye and chronicled in a family archive that contains much evidence of tragedy and human frailty.

Kennedy's early morning car crash on Capitol Hill this week was grist for comics and conservative bloggers even before the Rhode Island Democrat and police could sort through the particulars of what had happened. Kennedy initially blamed the accident on a reaction to prescription drugs that he was taking under a doctor's orders for a bout of stomach flu.

But he announced Friday that he was battling depression and an addiction to prescription drugs, and said he would immediately enter treatment at the Mayo Clinic in Rochester, Minn.

"I've been fighting this chronic disease since I was a young man," he said at a Capitol Hill news conference.

The six-term congressman, who was treated for alcohol and cocaine abuse as a teenager, in years past tied his problem to the pressures of growing up as a Kennedy.

"It was me hitting the wall and coming to grips with a lot of unanswered questions about who I am, where I came from, and how I was going to be accepted," he told The Boston Globe in 1999. "I didn't feel like I measured up to my family and who I was supposed to be."

For Patrick Joseph Kennedy, named after a great-great-grandfather who was the first Kennedy elected to office in America, there is so much to measure up to. President John Kennedy was Patrick's uncle; so was senator and attorney general Robert Kennedy. His father is Massachusetts Sen. Edward Kennedy. A cousin, Joseph Kennedy, served six terms in Congress. Another cousin, Kathleen Kennedy Townsend, served two terms as Maryland's lieutenant governor.

"Being a Kennedy is a double-edged sword," said Brown University's Darrell West, who wrote a biography of Patrick Kennedy. "You have opportunities that other people don't have but you live your life in the public spotlight and I think that's really been very hard for the younger generation.

"They have to live up to John, Robert and Ted Kennedy. Those are tough acts to follow."

Along with the record of public service, the Kennedy legacy is marked by addiction and other problems.

Edward Kennedy's name will forever be tied to the Chappaquiddick scandal of 1969, when his car ran off a bridge, killing his passenger, Mary Jo Kopechne. Kennedy did not immediately report the tragedy, and later pleaded guilty to leaving the scene of an accident.

Patrick's mother, Joan Kennedy, has long struggled with alcoholism and has been arrested several times for drunken driving. In 2004, her children took temporary guardianship of her affairs. Last year, she was found sprawled on a Boston sidewalk in the rain, and was hospitalized with a concussion and a broken shoulder.

One of Robert's sons, David, died in 1984 of a drug overdose. Robert Jr. was arrested in 1970 for marijuana possession and again in 1983 after nearly overdosing on heroin. Another of RFK's sons, Michael, was accused of having an affair with his family's teenage baby sitter. Michael died in 1997 when he ran into a tree while playing touch football on skis.

John Kennedy Jr. was killed in 1999 when his small plane crashed off Martha's Vineyard, Mass.

William Kennedy Smith, another Kennedy cousin, was tried and acquitted of raping a woman in 1991 at the family's Palm Beach estate. On the weekend of the alleged rape, Edward Kennedy had roused his nephew to visit some nightclubs.

The senator, who testified at the rape trial, apologized for "faults in the conduct of my personal life."

In his book Sons of Camelot, Laurence Leamer wrote that of all the Kennedy grandsons, "none seemed less able to compete than Ted and Joan's youngest son Patrick." As a youth, Leamer wrote, Patrick had an asthmatic condition that "if not psychosomatic, was clearly exacerbated by the tensions within his family. He had a father who he feared might be assassinated, a mother who moved in and out of an alcoholic haze, in and out of rehab, and in and out of emotional constancy."

Still, Patrick Kennedy forged ahead with a political career, serving as a state legislator by age 21 and a congressman by 27. He passed up a chance to run for the Senate in 2006, despite encouragement to do so from his father.

On Friday, as he announced plans to seek treatment, the family talk was all about rallying around one who was in trouble.

Patrick thanked his "loving family" for standing by him.

His father said he felt "pride and respect for a courageous man who has admitted to a problem and taken bold action to correct it."

Copyright 2006 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.