U.S. Rep. Patrick Kennedy, the drug-abusing son of Massachusetts Democratic Sen. Edward Kennedy, has been released from a drug rehabilitation program a month after crashing his car into a cement barrier and admitting a dependency on prescription drugs.

Kennedy, who has acknowledged he suffered from depression and had abused alcohol and prescription drugs for years, vowed on Monday to shun all “mood-altering drugs,” a promise he made after a similar trip to drug rehab late last year, but he still insists he did not receive preferential treatment from police.

The nephew of President John F. Kennedy crashed his car into a security barrier in Washington on May 4. He has said he was disoriented from sleeping pills and other medication.

Kennedy, 38, appeared with red, watery eyes, slurred speech and unsteady balance after the accident — his second in three weeks — but no sobriety tests were conducted at the scene. He was charged with three driving violations and driven home.

“Every day I’m on my knees thanking God that I didn’t hurt somebody,” he told a news conference, describing the crash as a wake-up call to seek help after suffering from alcohol and chemical dependency nearly his entire life.

Rhode Island Democrats have endorsed him for re-election but the state Republican Party said he should consider resigning because there was no guarantee that he will be able to do his job effectively.

“The Kennedy name seems to have maintained much of its luster, however illogical as it may seem under the circumstances,” said Chuck Newton, state Republican Party spokesman.

Kennedys have been prominent in American politics for decades. Kennedy’s uncles included John Kennedy, assassinated in 1963, and Robert Kennedy, a former U.S. attorney general who was assassinated in 1968 during his run for president.

Patrick’s father, Ted Kennedy, is a powerful liberal voice in the Senate and one of the longest-serving senators.

Several family members have had much-publicized drug and alcohol problems.

After speaking at a Brown University forum on mental health on Monday, Kennedy said he was not drinking on the night of the accident, but had taken Ambien, an insomnia drug, and Phenergan, an anti-nausea medication for gastroenteritis.

Kennedy, who is not married, said he had participated in a vote in Congress the previous evening until about 9:15 p.m. The next morning, he awoke at about 2:45 a.m. and told a female companion he needed to return to Congress to vote, he said.

He said he does not recall anything after that.

The Mayo Clinic said Kennedy had finished his treatment but might need to return for follow-up visits later. Kennedy was also a patient last winter at the clinic.

“This is a personal battle but it’s going to be on a very public stage,” he said.

It is not the first bout of negative publicity for Kennedy. In 2000, he shoved a female Los Angeles airport security guard into a metal detector. The woman sued and Kennedy agreed to pay an undisclosed sum and apologize in a settlement in 2002.

Also in 2000, Kennedy was accused of trashing a yacht.

According to a police report of the May incident, Kennedy’s 1997 Ford Mustang was traveling “at a high rate of speed” before swerving into the wrong lane and hitting the barrier.