WASHINGTON - A college dropout from Florida. A nurse's aide from Denver. The owner of a pizza-and-wings joint from upstate New York.

Except for their embrace of Islam, there's no common profile for the 100-plus Americans who have traveled to Syria to join Islamic fighters or are accused of supporting them from the United States.

Their reasons for joining an extremist cause a half-world away are as varied as their geography and life stories.

Some seek adventure and camaraderie. Others feel a call to fight perceived injustice.

But a common strain of disaffection, a search for meaning, seems to emerge, at times stronger than any motivation tied to religious devotion.

"What unifies all these folks is a desire to be recognized, a desire to find a cause that they can mold their life to," says Evan Kohlmann, who tracks terrorists with Flashpoint Global Partners.

Foreign fighters from dozens of nations are pouring into the Middle East to join the Islamic State group and other terrorist organizations. U.S. officials are putting new energy into trying to understand what radicalizes people far removed from the fight, and into trying to prod countries to do a better job of keeping them from joining up.

On Wednesday, President Barack Obama will lead a meeting of the 15-member U.N. Security Council as part of the effort to stem the flow of foreign nationals. Next month, the White House will hold a conference on the radicalization of Americans.

It's an increasingly urgent matter now that the U.S. and allies are directly attacking Islamic State fighters. There are concerns of blowback that encourages more terrorism at home.

Just last week, a post on a top jihadi forum urged American Muslims who can't reach the battlefront to wage "an aggressive and sustained campaign of lone-wolf attacks" locally, according to the SITE Intelligence Group. As well, there are worries that fighters with U.S. passports will return home to carry out attacks in America or with airplanes headed to the U.S.

The transition from everyday American to foreign fighter for a group that trumpets the beheading of its enemies may start with concern that fellow Muslims are being killed abroad. It often includes Internet chatrooms and online conversations with extremists. It may involve knowing someone who's radicalized. Many cite the teachings of radical U.S.-born cleric Anwar al-Awlaki, who was killed in a U.S. drone strike in Yemen in 2011 but whose words are still influential in cyberspace.

Moner Mohammad Abusalha, 22, who grew up playing basketball in Vero Beach, Fla., described his journey to jihadism in a video before he killed himself and 16 others in a suicide bombing in Syria last May. He mentioned both the teachings of al-Awlaki and the influence of friend.

The college dropout, whose father was Palestinian and mother was Italian-American, said of his life as a Muslim in America: "This never was a place for me. ... I was always sad and depressed. Life sucked."

"I want to rest in the afterlife, in heaven," he said. "Heaven is better."

Shannon Conley, 19, a nurse's aide from suburban Denver, wanted to marry an Islamic extremist fighter she met online and thought she could use her U.S. military training to fight a holy war overseas. In pursuing her Muslim faith, "she was exposed to teachings through which she was terribly misled," her lawyer, Robert Pepin, wrote in a court filing. Conley pleaded guilty to trying to help Islamic militants and is awaiting sentencing.

In the most recent case, 30-year-old Mufid Elfgeeh, a pizza and food mart owner from Rochester, N.Y., was indicted last week for trying to help three people travel to Syria to join extremist fighters. A naturalized citizen from Yemen, Elfgeeh was arrested this year for buying guns as part of a plan to kill U.S. service members.

Elfgeeh has pleaded innocent.

While the ranks of foreign fighters from America include both naturalized citizens and the native-born, Kamran Bokhari of Stratfor global intelligence said second-generation Muslim Americans trying to balance two cultures could be particularly vulnerable.

"It's natural for the second generation to be feeling sort of lost and not knowing who they are," he said. They may feel drawn to the plight of Muslims abroad, and feel guilty about living comfortable lives, he added.

For all the concern about Americans who support Islamic militants, terrorism experts say the problem is much worse in Europe, where Muslims are not as wealthy or assimilated. Several hundred people from Britain have traveled to Syria, according to official estimates, and France and Germany have estimated a combined 1,300 of their citizens have joined the fight.

Aaron Zelin, an expert on jihadi groups at the Washington Institute for Near East Policy, said roughly half the Americans who have joined the Islamic State group are converts to Islam. The rest typically are born Muslim or "reverts," people who were Muslim at birth, but didn't practice the faith until later in life, he said.

"I would argue that they converted to jihadism, not necessarily mainstream Islam," he said.

Attorney General Eric Holder pointed to the indictment of Elfgeeh as evidence that U.S. officials are aggressively working to identify and disrupt those who want to join or support terrorist groups.

Critics say the administration's efforts have been largely cosmetic and that officials haven't done enough to understand root causes.