Why some people's brains can't "switch off" at night
Australian scientists have found convincing evidence that insomnia is associated with disturbances in the natural circadian rhythm of mental activity. This helps to explain why some people have quiet thoughts in the evening, while others "run around in circles" until deep into the night.
The University of South Australia study was the first to compare how thought patterns change overnight between people with chronic insomnia and those who sleep normally. The results are published in the journal Sleep Medicine.
How the study was conducted
The scientists observed 32 elderly participants (16 with insomnia and 16 with good sleep) for 24 hours under strict laboratory control:
participants stayed in bed the entire time,
in a semi-dark room,
with strictly regulated meals and minimal activity,
but they had to remain awake.
Every hour they completed questionnaires assessing:
the nature of their thoughts (business, emotional, distracted),
their "tone" and their emotional colouring,
how easy or difficult it was to control the flow of thoughts.
Such a regime allowed us to remove external factors (light, routines, gadgets) and see how the internal "clockwork" of the brain works.
What they found
Both healthy people and insomniacs showed daily fluctuations in mental activity:
- maximum in the afternoon/evening, minimum in the morning.
But the insomnia group turned out to have a few important differences:
In the "good sleepers," by nightfall, the thinking mode shifted naturally from daytime "problem solving" to mental "letting go" and decreased engagement.
In people with insomnia, this transition was much weaker:
their thoughts remained more "daytime" - focused, fixated on problems and emotions - even during hours when the brain should be "quiet."The insomniacs' peak cognitive activity was shifted about 6.5 hours later, meaning their internal "clock" seemed to be pushing their brains to think actively well past midnight.
"Sleep is not just about closing your eyes," emphasises Professor Kurt Lashington. - The brain needs to switch off from focused thoughts and emotional involvement. In insomnia, this process is dulled and delayed, probably due to disturbances in circadian rhythms."
What this means for treatment
The authors believe the results open up new therapeutic possibilities:
amplification of circadian rhythms - with properly selected light therapy,
structured daily routines (stable rising, activity and eating times),
mindfulness and relaxation practices that help to "let go" of thoughts before going to sleep.
Most techniques for insomnia now focus on behaviour (sleep hygiene, cognitive behavioural therapy). New evidence suggests that personalised approaches that take into account both circadian and cognitive characteristics may be more effective.