Divergent Gray Matter Changes in Insomnia Disorder: Anxiety-Linked Hypertrophy and Sleep-Related Atrophy

Insomnia disorder, the most prevalent sleep disorder in adults, is highly comorbid with anxiety and exhibits a well-established bidirectional relationship. Nevertheless, the neuroanatomical differences between insomnia disorder patients with and without anxiety remain unclear. This study aimed to investigate these distinctions and their clinical associations. We enrolled 111 insomnia disorder patients and 57 healthy controls. All participants underwent magnetic resonance imaging and clinical assessments. Patients were classified into insomnia disorder with anxiety and without anxiety groups based on their Self-Rating Anxiety Scale scores. Gray matter volume was examined using Diffeomorphic Anatomical Registration Through Exponentiated Lie Algebra Voxel-Based Morphometry. Analysis of covariance and partial correlation analyses were conducted to compare the differences between groups and to assess clinical relationships. Limitations include the cross-sectional design, which prevents causal inference, and the reliance on subjective sleep measures. Despite these, we identified a dual pattern of structural reorganization influenced by anxiety comorbidity. Our findings offer novel neuroimaging biomarkers for insomnia disorder subtyping and substantially enhance the understanding of the neural mechanisms underlying insomnia disorder and anxiety comorbidity.