Comparing Executive Function Impairments (Inhibition, Shifting, and Updating Information) Between Inpatient, Outpatient, Subclinical Depressed Patients, and Control Groups

Previous research has reported executive function impairments an underlying deficit in developing depressive symptoms in depressed individuals. However, the relationship between executive function impairments and depression has remained inconclusive. Although many studies have found significant deficits associated with major depressive disorder on neuropsychological measures of executive functions, others have not, potentially due to the severity of depression, which is not considered an essential factor in executive function deficits. Also, one of the reasons for disagreement is the lack of objective diagnostic criteria for the severity of depression in these patients. Previous research has considered the clinical status of depressed patients an essential criterion in the severity of the disorder. Given these conditions, the present study compared the executive functions of inhibition, shifting, and updating information in inpatient, outpatient, and subclinical depressed patients and the control groups.

The study method was causal–comparative. All samples were selected by available sampling based on inclusion and exclusion criteria. From the statistical population of depressed patients admitted to Shahid Beheshti Psychiatric Hospital in Zanjan City, Iran, in 2020–2021, 46 patients were selected. A total of 68 people were selected from the statistical population of depressed outpatients referred to the outpatient clinic in 2020–2021. From the statistical population of Zanjan in 2020–2021, 65 people were selected for the subclinical group and 66 people for the control group. Research assessment tools included the Beck Depression Inventory–II (Beck et al., 1996), the Structured Clinical Interview for DSM–5 (First et al., 2016), the Computerized version of the Stroop Color–Word Test (Stroop, 1935), the Wisconsin Card Sorting Test (Grant & Berg, 1948), and the N–Back Test (Kirchner, 1958). The data of this study were analyzed using descriptive statistics (mean & standard deviation). Also, in the inferential statistics section, the Chi–square test, The Kruskal–Wallis test, multivariate analysis of covariance (MANCOVA), 1–way analysis of covariance (ANOVA), and LSD post hoc test were used. The significance level of the tests was considered 0.05. All analyses were performed using SPSS software version 23.

The multivariate analysis of variance showed a significant difference between the studied groups in the components of executive functions (p<0.001). The ANOVA showed that the groups of depressed outpatients (p=0.008) and depressed inpatients (p<0.001) had a significant difference from the control group in the "incongruent response time" as an inhibition measurement index. However, no significant difference was found between the subclinical depressed and control groups (p=0.125). Also, in the paired comparison between all three depressed groups, there was a significant difference (p<0.001). Still, no significant difference was found between the outpatient and the inpatient depressed groups (p=0.062). There was a significant difference between all depressed groups and the control group in the "number of categories completed" and "perseverative error" as shifting measurement indices (p<0.05). Also, there were significant differences in the paired comparisons between all three groups of depressed people (p<0.05). However, no significant difference was found between the subclinical and outpatient groups (p>0.05). There was a significant difference between the inpatient depressed group and the control group regarding the "correct answer" and "average response time" as indices of evaluation of updating (p<0.001). However, no significant difference was found between the subclinical and outpatient depressed groups with the control group (p>0.05). Also, in the paired comparison between all three groups of depressed people, the inpatient depressed group showed a significant difference with the subclinical and outpatient depressed groups in the "correct answer" and "average response time" (p<0.05). A significant difference was also found in the "correct answer" between subclinical and outpatient depressed groups (p=0.034).

According to the study findings, depressed groups show weaker performance in all three components of executive functions compared to the control group. Also, in addition to the fact that executive functions are damaged in depressed people, in people with more severe symptoms of depression, executive functions are significantly weaker.