But millennials are also more motivated to plan for their financial future and savvy about how to do it, she said.
"They realize they will have to be the [primary] source for their retirement income over their working career," Stanzak said. "There are very few companies that provide pensions today, and Social Security is in question. Their retirement is in their hands."
Although Social Security is likely to remain a source of income for millennials in retirement, albeit a smaller one, the Social Security Administration projects it will have enough money from payroll taxes to cover three-quarters of benefits it has promised retirees after 2034, when its reserves are scheduled to run out . Many millennials say they aren't counting on it.
Nearly two-thirds of millennials surveyed by T. Rowe Price earlier this year said they believe they're more likely to win the lottery than to receive any money from Social Security. And a Northwestern Mutual survey found 73 percent of millennials expect to work past 65 because Social Security won't take care of their retirement needs.
That's not a bad thing, necessarily, said Stanzak, noting that they are quick to take advantage of 401(k) plans and company matches. "This is as important for millennials as it is for everyone."
Still, 4 in 5 millennials said retirement planning was their top financial challenge, according to Lincoln Financial Group's annual Measuring Optimism, Outlook and Direction (M.O.O.D.) of America survey. Indeed, many are not contributing as much as they should.
The rise of auto-enrollment programs and new streamlined sign-up processes have helped draw in more young workers: One report published this spring by BMO Retirement Services, for example, found participation rates among workers 25 to 34 years jumped 22 percent in plans with an automatic-enrollment feature. And for workers under 25, participation in auto-enrollment plans was more than double that of voluntary enrollment plans (29 percent versus 68 percent).
But while advisers typically recommend workers contribute 10 to 15 percent of their income (including any employer match), T. Rowe Price found in a recent study that the average default contribution rate for millennials was 3 percent.
Still, advisers are encouraged that many millennials are setting something aside, despite the financial planning challenges they face. About 83 percent of the millennials polled by Lincoln Financial said they save money from every paycheck, compared with 78 percent of the general population. (The Lincoln Financial Group polled 2,273 U.S. adults ages 18 and older.)
"Pensions and Social Security were nice because they delayed the need to start a retirement plan, but that landscape has changed for our generation," said Mike Salmon, a financial adviser — and a millennial — at Moisand Fitzgerald Tamayo in Orlando, Florida.
Salmon recommends millennials gradually increase the percent of savings, even by a percentage point or two. "The goal is always to save more."