Retirement is such a concern, it’s causing Americans to lose sleep—literally.

Fifty-six percent of Americans are losing sleep over retirement, according to a recent study by Ramsey Solutions in Nashville, Tenn., a financial education provider. 

Ramsey Solutions, affiliated with financial radio host and author Dave Ramsey, examined the link between retirement readiness, stress and sleep loss. Apparently, what really keeps Americans up at night is all in their heads: The study found that 8 in 10 Americans who feel ashamed, guilty or embarrassed about their retirement are losing sleep, yet less than half of those who feel excited or confident about their future are losing sleep.

Perhaps that’s because optimism about one’s future is strongly linked to retirement readiness: Nine in 10 survey respondents who felt confident about their future were focused on preparing for retirement.

Confidence and financial advice were also directly linked. Seventy percent of respondents confident about their future said they knew whom to ask about retirement questions. Respondents who were uncomfortable talking to a financial advisor were more likely to feel regret, guilt and shame about their retirement.

Still, what’s out of sight is out of mind: 64 percent of respondents who claimed to be active retirement savers said they were losing sleep over retirement, compared to 49 percent of non-savers.

The study implies that just thinking about one’s retirement future can cause stress and sleep loss, according to Ramsey Solutions. In the survey, 74 percent of Americans who reported being very concerned about their future claimed to lose sleep, compared with 17 percent who had no concerns about their future.

Sources of stress differed for savers and non-savers. Non-savers reported being most anxious about their children’s activities, needs and education, while savers reported anxiety around lack of planning and procrastination.

For the study, 1,016 U.S. adults were surveyed between February 26 and March 1.