Australian scientists have found strong evidence that insomnia may be caused by problems with the brain’s natural 24-hour cycle of activity.
This may explain why some people have trouble “switching off” their thoughts at night and falling asleep.
The new study, led by the University of South Australia, is the first to carefully track how thinking patterns change throughout the day in people with long-term insomnia, compared to those who sleep well. The study was published in the journal Sleep Medicine.
Insomnia affects about 10% of the general population and up to one-third of older adults. People with insomnia often say that they have an overactive or racing mind, especially at night. Scientists have suspected this is due to mental hyperactivity, but until now, they weren’t sure what caused it.
To find out more, researchers studied whether the brains of people with insomnia have abnormal circadian rhythms. Circadian rhythms are the body’s internal clock that tells us when to wake up, be alert, and go to sleep.
In the experiment, 32 older adults were monitored in a lab for 24 hours. Half of them had insomnia, and the other half were healthy sleepers.
Everyone stayed awake in a dimly lit room, lying in bed with no distractions. Food, noise, and movement were all carefully controlled. Every hour, participants answered questions about the quality and emotional tone of their thoughts.
Both groups showed daily ups and downs in mental activity. Thinking was most intense in the afternoon and quietest in the early morning. But people with insomnia had some key differences.
Healthy sleepers shifted from busy, goal-focused thinking during the day to calmer, less emotional thinking at night. But those with insomnia didn’t shift as much. Their minds stayed more active and daytime-like during the hours when the brain should be winding down.
In fact, their peak mental activity was delayed by more than six hours. This means their internal clocks may be keeping them alert far into the night.
Lead researcher Professor Kurt Lushington explained, “Sleep isn’t just about closing your eyes. It’s about the brain letting go of problem-solving and emotional thinking. In people with insomnia, this shift is weaker and happens later than normal.”
Professor Jill Dorrian, a co-author of the study, said the findings point to new ways of treating insomnia. One option is to help people reset their body clocks using light exposure or regular daily schedules. Mindfulness techniques could also help calm the mind at night.
Right now, most insomnia treatments focus on changing behavior—like getting out of bed if you can’t sleep or avoiding screens before bedtime. But this study suggests that addressing the brain’s timing system could also be important.
By helping the brain follow a stronger day-night rhythm, doctors may be able to reduce nighttime overthinking and help people sleep better.
If you care about sleep, please read studies about herb that could help you sleep well at night, and these drugs could lower severity of sleep apnea by one third.
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