"Usama, your mama." 

It might sound simple, but that line brought the house down recently at Gotham Comedy Club in Manhattan. 

Six weeks after the terrorist attacks on the U.S., the "laughter as therapy" adage is ringing especially true. Comedians find they're playing a crucial — but tricky — role in a society mired in sadness and fear. 

"In some ways it's hard, but in some ways it's easier because everybody identifies with this," said stand-up comedian Colin Quinn, of Saturday Night Live fame. "I wouldn't put us up there with the guys flying C-130s over no-fly zones, but we're providing a way for people to deal with it and get a few laughs." 

Psychologist Steven M. Sultanoff, former president of the Association for Applied and Therapeutic Humor, said comedians have had to perform a difficult balancing act since the Sept. 11 disaster. 

"They have to integrate humor so it's non-offensive but healing," Sultanoff said. "It becomes very challenging for the Lenos and the Lettermans to try to hit that middle ground." 

Sultanoff said humor is therapeutic because it incites laughter and the positive biochemical reactions that accompany it. It also changes a person's emotional state and perception of the world. 

"I would put humor up there with empathy as being very powerful to the human condition," he said. 

But tailoring comedy routines at such a sensitive time hasn't been easy. Audiences have seen comedians struggle — and have witnessed an evolution in their acts. 

"For a while, people felt guilty about laughing," said Chris Mazzilli, co-owner and founder of Gotham. "Comics were kind of tiptoeing around things." 

Mazzilli said he closed his club, which is about two miles from the World Trade Center, the week of the disaster, but reopened it the following weekend. 

"If they wanted to laugh, I wanted to provide that service for them," he said. "As sad as people were, they would come up to me afterwards and say, 'Thanks for opening. It took our minds off it for a little while.'" 

Initially, even comedians didn't even feel like chuckling as they coped with their own grief and shock along with the rest of the country. 

"I didn't go on for a week afterwards because I felt sick to my stomach," said Quinn, a Brooklyn native. 

But Mazzilli said he was amazed at comedians' resilience in the early days of the crisis. 

"They were very, very sad too, but they had to get up there and do their thing," he said. "It's hard to make people laugh when you're hurting on the inside yourself." 

The first late-night shows that aired after the catastrophe were uncharacteristically somber. Hosts like Jay Leno and David Letterman opted for segments with quip-free discussions about the news and guests such as CBS Evening News anchorman Dan Rather. 

"There was almost a national outcry that it was politically incorrect to use humor during that time of extreme mourning," said Sultanoff. "There was such a trauma and shock to the system, many people didn't want to feel any kind of humor. Comedians were scrambling, saying, 'What do I do?'" 

Within a week or so, comedians tried innocuous, silly jokes, unrelated to anything going on in the world. Letterman's first "Top 10" list was about words that almost rhyme with "hat." 

"It was totally absurd. It couldn't in any way offend anyone," Sultanoff said. "Being that it was so ridiculous, it was funny but also safe." 

Recently, comedians have started amusing audiences with anti-terrorist jabs and anthrax banter — but they're still careful about what they say. 

"Whatever they're doing on stage is being done with caution," Mazzilli said. 

Quinn said he's made light of the fact that President Bush has repeatedly called the terrorists "evildoers," joking it's because he's limited to non-obscenities on national television. 

"He says to his speech writers, 'Evildoers? What am I, Aquaman?'" Quinn quipped. "His speech writers used to work for Marvel Comics." 

Quinn also kidded about what catch phrase the President might use next. 

"He could say, 'These knuckleheads really get my goat.'"