By Candy Gibson, University of South Australia
February 24, 2026

Insomnia may be driven by delayed circadian rhythms that prevent the brain from powering down at night.

Australian scientists have uncovered strong evidence that chronic insomnia may stem from disruptions in the brain’s internal 24-hour cycle of mental activity. The findings help explain why some people find it so difficult to “switch off” at night, even when they are physically tired.

In a study published in Sleep Medicine, researchers from the University of South Australia (UniSA) tracked how thinking patterns rise and fall across the day in people with long-term insomnia compared with healthy sleepers. This is the first study to chart daily cognitive rhythms in this way.

Insomnia affects roughly 10% of the population and up to one-third of older adults. Many people with the condition describe their minds as overactive or constantly racing at night.

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When disengagement is delayed

“Sleep is not just about closing your eyes,” Prof Lushington says. “It’s about the brain disengaging from goal-directed thought and emotional involvement.”

“Our study shows that in insomnia, this disengagement is blunted and delayed, likely due to circadian rhythm abnormalities. This means that the brain doesn’t receive strong signals to ‘power down’ at night.”

Co-author, UniSA Professor Jill Dorrian, says the findings highlight new treatment possibilities for insomniacs, such as interventions that strengthen circadian rhythms.

“These include timed light exposure and structured daily routines that may restore the natural day-night variation in thought patterns,” Prof Dorrian says.

“Practicing mindfulness may also help quiet the mind at night.”

The researchers say that current treatments often focus on behavioral strategies, but these findings suggest that tailored approaches addressing circadian and cognitive factors could offer a solution.

Reference: “Cognitive-affective disengagement: 24h rhythm in insomniacs versus healthy good sleepers” by Kurt Lushington, Jillian Dorrian, Hans P.A. Van Dongen and Leon Lack, 25 October 2025, Sleep Medicine.
DOI: 10.1016/j.sleep.2025.106881
https://doi.org/10.1016/j.sleep.2025.106881