Why do we get anxious thoughts before bed?

MINNEAPOLIS — Right as people get comfortable at night in bed, discomfort can begin in their minds. Suddenly, they’re stuck on a thought and struggling to sleep.
It’s ironic that in a place and time meant for rest — our beds — anxiety-inducing thoughts prevent its purpose.
“The main part of not being able to go to sleep is because we worry,” said Steven Dukes, of Minneapolis.
Dwelling on the past and stressing about the future before we sleep share a common problem.
“There really isn’t an endpoint, and the lack of endpoint keeps the wheels just churning and churning,” said Dr. Mark Rosenblum. He’s a sleep psychologist with Hennepin Healthcare. “For many people at nighttime, that’s the first time they’re not really distracted by anything.” 
Work, family and activities give our minds something to focus on during the day, but they’re gone once we lay in bed. The quiet solitude allows thoughts to occupy the mind.
“The anxiety is what really picks up the most,” said Dukes.
“Anxiety oftentimes are things that may happen in the future or have not happened,” said Rosenblum. Thinking about events in the future creates uncertainty. The uncertainty can lead to an anxious loop where the person plays out several scenarios in their head, cycling them over and over.
“Then I worry that I’m not getting enough sleep to deal with the things that I’m worried about the next day,” said Hokkanen.
How can we stop our minds from racing while in bed? Rosenblum suggests mindfulness meditation, which means relaxing and focusing on whatever we’re doing. 
“For example, if I’m deep breathing, I’m not thinking about what’s coming up tomorrow. I’m thinking of the sensation of my lungs inhaling and exhaling,” he said.
How can we prevent our thoughts from racing? Rosenblum has three suggestions. 
Rosenblum said people diagnosed with anxiety are more prone to insomnia, and that those diagnosed with insomnia are more prone to anxiety. Those who have both disorders are advised to seek professional help for each one.