Background: The neurological correlates of Generalised Anxiety Disorder (GAD) are not well known, however there\nis evidence of cortical dysregulation in patients with GAD. The aim of the study was to examine cortical functional\nactivity in different cerebral regions in patients with GAD using electroencephalogram (EEG) nonlinear analysis to\nevaluate its contribution of anxiety severity.\nMethods: The cohorts consisted of 64 patients diagnosed with GAD as classified by the Structured Clinical\nInterview for the Diagnostic and Statistical Manual of the American Psychiatric Association-IV-TR. Anxiety severity was\nassessed using the Hamilton Rating Scale for Anxiety (HAMA) severity score, with 7 � scores � 17 indicating\nmild anxiety as A group (n = 31) and 18 and above indicating moderate-severe anxiety as B group (n = 33).\nParticipants with clinical levels of depression symptoms were excluded. A healthy control group comprising\n30 participants was matched for age and gender. Closed eyes EEGs were conducted, and between-group\ndifferences on non-linear parameter Correlation Dimension (D2) were analyzed. The association of D2 value\nwith HAMA scores was analyzed using multiple linear stepwise regression.\nResults: Compared with the control group, D2 values were increased in anxiety groups (P < .05). For those\nwith mild anxiety, this difference occurred in the left prefrontal regions (P < .05). For those with moderate-severe\nanxiety, significantly greater D2 values were observed in all of the cerebral regions, especially in the left cerebral\nregions and right temporal lobe (P < .01). When compared with those with mild anxiety, D2 values were significantly\ngreater for those with moderate-severe anxiety in the right temporal lobe and all left cerebral regions except\nfor left occipital lobe (P < .05). A positive correlation was observed between D2 values and moderate-severe\nanxiety HAMA scores.\nConclusions: The increased D2 values were found in the majority of cerebral regions in GAD patients, especially in\nthe left cerebral regions and the right temporal lobe. The increased GAD severity positively correlates to the D2 values\nin a larger number of cerebral regions. This analysis method can potentially be used as a complementary tool\nto examine dysfunctional cortical activity in GAD.
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