We’ve all been there. Lying awake in our beds, unable to shed the worries and stresses of the day or days to come when we should be peacefully drifting off to dreamland. For some of us, this is an unfortunate nightly ritual.
New research shows that people with chronic difficulties getting to sleep may suffer from a disruption in the brain’s ability to transition from aroused, daytime problem solving to necessary, nightly downtime, a 24-hour cycle. In short, the brains of insomniacs fail to disengage at the appropriate hour, continuing to process the concerns of the day well past bedtime.
A team of sleep scientists from universities in Australia and the United States published their findings in Sleep Medicine.
The researchers monitored 32 older adults—16 healthy sleepers and 16 insomniacs—over the course of 24 hours. During this period, the participants were isolated in beds without environmental or behavioral signals to alert them to time of day. This dimly-lit setup, in effect, meant that the volunteers’ brain activity—which the scientists assessed hourly through checklists that captured data on the quality and controllability of their thoughts—was influenced exclusively by the internal, circadian rhythms that pulse through us all.
Read more: “How Your Body Knows What Time It Is”
By observing these different sleepers, the scientists found that they all had natural peaks of brain activity in the afternoon and valleys in the early morning hours. But people who had trouble drifting off to sleep failed to transition effectively between these two states. “Unlike good sleepers, whose cognitive state shifted predictably from daytime problem-solving to nighttime disengagement, those with insomnia failed to downshift as strongly,” said University of South Australia clinical psychologist and co-author Kurt Lushington in a statement. “Their thought patterns stayed more daytime-like in the nighttime hours when the brain should be quietening.”
The problem, Lushington and his colleagues suggested, could be that the insomniacs’ circadian rhythms were shifted by hours. “Our study shows that in insomnia, this disengagement is blunted and delayed, likely due to circadian rhythm abnormalities,” Lushington added. “This means that the brain doesn’t receive strong signals to ‘power down’ at night.”
Some of the limited number insomniacs in the study did display distinct trait-like differences in thought structure, with high levels of sequential thinking—which typically indicates step-wise problem solving and activates the brain’s language and decision-making centers but can be indicative of depression and anxiety—dragging on into sleeping hours. But the abnormalities in circadian rhythms suggested by the findings open the door to more tailored interventions for people whose minds don’t stop racing once their heads hit the pillow. “These include timed light exposure and structured daily routines that may restore the natural day-night variation in thought patterns,” said University of South Australia sleep psychologist and co-author Jill Dorrian.
Whatever keeps any of us from entering the restorative kingdom of sleep on a nightly basis, it’s good to know that there are scientists out there probing the rhythm of our thoughts for clues to help us get some shuteye. 
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