Tom Williams via Getty Images Rep. Dana Rohrabacher (R-Calif.) is an avid surfer. But he said the sport gave him shoulder pain and arthritis, and he turned to cannabis for relief.

Rep. Dana Rohrabacher (R-Calif.), a leading voice for the reform of marijuana laws in the United States, became the first sitting member of Congress in recent history to admit to medical marijuana use.

Rohrabacher, speaking to a group of cannabis activists on Tuesday on Capital Hill, said he has been an avid surfer for about three decades but had not been able to enjoy the sport for about a year and a half due to arthritis pain he's developed in his shoulder. The pain became so severe that it has disrupted his sleep, the lawmaker said.

That is, until he tried medical marijuana.

“I went to one of these hempfests or something like that they had in San Bernardino,” Rohrabacher said, as first reported by Russ Belville at Cannabis Radio.

At the hemp festival, he met a vendor who introduced him to a cannabis-infused topical rub.

“This guy was showing me the medical things and all that, and he says, ‘You should try this.’ And it’s a candle and you light the candle, and the wax is in there and it melts down, and then you rub it on whatever you’ve got problems with,” the Republican congressman said.

He finally tried the product a couple of weeks ago, and that was "the first time in a year and a half that I had a decent night's sleep because the arthritis pain is gone."

The attendees cheered his comments.

Rohrabacher, a vocal supporter for reform of the nation's marijuana laws, is one of the main sponsors of a measure that blocked the Department of Justice from using funds to target and prosecute medical marijuana patients or businesses who are operating legal in their state. The amendment has been reauthorized for the past two fiscal years.

"Now don't tell anybody I broke the law, they'll bust down my door and take whatever's inside and use it as evidence against me, whatever it is," Rohrabacher said. "The bottom line is, there's definitely cannabis in there and it makes sure that I can sleep now."

Listen to Rohrabacher's full remarks at Cannabis Radio.

This was the first time Rohrabacher has spoken publicly about using medical cannabis, his press secretary Ken Grubbs told The Huffington Post.

It was also the first time in recent history that a sitting congressman admitted to using medical marijuana, said Marijuana Majority founder Tom Angell.

"Putting a face on the people who use marijuana will help immensely in the battle to end criminalization and other forms of harmful discrimination," Angell added. "It’s now going to be much harder for members of Congress, particularly those in the GOP caucus, to vote against medical marijuana, since they now know that one of their friends and colleagues is directly benefiting from it."

California, along with 23 other states and the District of Columbia, has legalized medical marijuana. This year, voters in four more states are expected to consider doing the same via ballot initiative. Attitudes toward the plant and strict prohibition policies have rapidly shifted in recent years. An April CBS News poll found that 90 percent of Americans support the use of marijuana for medical purposes, with 56 percent in support of legalization for recreational use.

CORRECTION: An earlier version of this article misspelled Russ Belville's last name.