The insomnia disorder subtype with objective short sleep duration (ISS) exhibited greater cortical thickness than the normal sleep duration subtype (INS) in multiple right-hemisphere regions, with negative correlations found between cortical thickness and total sleep duration.
The ISS phenotype showed greater cortical thickness than the INS phenotype in the right lateral orbital frontal cortex.
The ISS phenotype showed greater cortical thickness than the INS phenotype in the right postcentral gyrus.
The ISS phenotype showed greater cortical thickness than the INS phenotype in the right inferior temporal gyrus.
The ISS phenotype showed greater cortical thickness than the INS phenotype in the right superior frontal gyrus.
The ISS phenotype showed greater cortical thickness than the INS phenotype in both the right and left paracentral lobules.
No significant differences between ISS and INS phenotypes were found in gray matter volume, gyrification index, sulcus depth, or fractal dimension.
Cortical thickness in the identified regions was negatively correlated with total sleep duration.
This research suggests that people with insomnia who also objectively sleep for shorter durations (measured rather than self-reported) have structural differences in their brain's outer layer (cortex) compared to people with insomnia who sleep normal amounts. Specifically, the short-sleeping insomnia group had a thicker cortex in several regions, mostly on the right side of the brain, including areas involved in emotion, sensation, and thinking. Interestingly, other brain structure measures like overall gray matter volume and brain folding patterns did not differ between the two groups, suggesting that cortical thickness may be particularly sensitive to the effects of shortened sleep in insomnia. The study also found that the less total sleep a person got, the thicker their cortex tended to be in these regions — an unexpected direction, since thicker cortex is not always associated with worse health. This was a relatively small study with 55 participants (22 in the short-sleep group), and the authors caution that these are preliminary findings that cannot establish a definitive cause-and-effect relationship. This research matters because it supports the idea that insomnia with objectively short sleep is a biologically distinct subtype with measurable brain differences, which could eventually help guide more targeted treatments. The authors call for larger studies to confirm and better understand these brain structural patterns.
Yang K, Ran B, He D, Guo Z, Jiang B. (2026). Cortical morphology of insomnia with objective short sleep duration phenotype.. Sleep & breathing = Schlaf & Atmung. https://doi.org/10.1007/s11325-025-03495-w