Effects of Comorbidity of Generalized Anxiety Disorder on Executive Functions of Patients with Major Depressive Disorder: A Multi-center Retrospective Case-control Study

  Objective  To analyze the effect of comorbidity of generalized anxiety disorder (GAD) at different levels on executive functions (EFs) of patients with major depressive disorder (MDD).

  Methods  Data of MDD patients and healthy controls in three general hospitals from February 2014 to January 2016 were retrospectively collected. Hamilton anxiety scale (HAMA) was used to evaluate the level of anxiety. MDD patients were grouped into MDD+GAD or MDD-GAD based on the result of the mini-international neuropsychiatric interview (MINI). EFs were evaluated by the animal fluency test (AFT), brief assessment of cognition in schizophrenia-symbolic coding (BACS-SC), color trail test (CTT), and Stroop color word test (SCWT) from MATRICS consensus cognitive battery (MCCB). We compared the EFs of different groups, and then explored the relevance between the level of anxiety and EFs by Spearman analysis.

  Results  A total of 230 MDD patients and 77 healthy controls (G0: HC) were included. There were 86 comorbid with GAD (G1: MDD+GAD), 144 without GAD (G2: MDD-GAD). AFT, BACS-SC, CTT and SCWT results were lower in G1 and G2 than in G0(all P < 0.05). G1 had better AFT results than G2 (P < 0.05), while the difference in the results of BACS-SC, CTT and SCWT were unremarkable between G1 and G2 (all P > 0.05). MDD patients with mild anxiety symptoms (7 < HAMA≤14) had statistically significant lower scores in AFT, BACS-SC and SCWT than those with moderate (14 < HAMA≤29) or severe (HAMA > 29) anxiety symptoms (all P < 0.05), while no significant difference in test results were found between the subgroups of moderate and severe anxiety (all P > 0.05). Spearman analysis showed HAMA scores were relevant with AFT, BACS-SC and SCWT results (AFT: r_s=0.26, P < 0.001; BACS-SC: r_s=0.26, P < 0.001; SCWT: r_s=0.27, P < 0.001), but irrelevant with CTT results (r_s=-0.11, P=0.106).

  Conclusions  Comorbidity of GAD may alleviate deficits of verbal fluency in MDD patients. MDD patients with anxiety at a higher level tend to have better executive functions such as verbal fluency, information processing speed, and inhibition.