Reduced gray matter in the prefrontal cortex and hippocampus: a potential neuroanatomical feature of insomnia comorbid with anxiety.

BACKGROUND: Chronic insomnia disorder (CID) frequently comorbid with generalized anxiety disorder (GAD), and accurate identification of this comorbidity remains challenging. Neuroimaging-based gray matter measurements may provide objective features to improve precise identification. OBJECTIVE: To investigate the potential value of gray matter features in distinguishing CID comorbid with GAD from CID or GAD alone. METHODS: Voxel-based morphometry (VBM) and surface-based morphometry (SBM) were used to assess gray matter features. Comparisons were conducted among patients with CID (n = 46), GAD (n = 44), CID comorbid with GAD (n = 43), and healthy controls (n = 45). RESULTS: CID comorbid with GAD was characterized by reduced gray matter volume in the prefrontal cortex and hippocampus. CID was characterized by reduced hippocampal volume and increased gyrification index (GI) in the prefrontal cortex. GAD was characterized by increased regional prefrontal cortex volume. These neuroanatomical features were associated with disease severity. CONCLUSION: Distinct gray matter features were observed among CID, GAD, and CID comorbid with GAD. These findings suggest that gray matter features may contribute to the identification of these conditions.