Executive Function in Students with Depression, Anxiety, and Stress Symptoms 

Bita Ajilchi¹, Vahid Nejati^*2

¹Department of Psychology, Faculty of Human Science, Science and Research Branch University, Islamic Azad University (IAU), Tehran, Iran

^{2 *}Department of Psychology, Faculty of Human Science, Shahid Beheshti University, Tehran, Iran

Corresponding Author Email: Nejati.sbu.ac.ir

Abstract:

This study was to investigate the executive functions of students with depression, anxiety, and stress symptoms in comparison to those of healthy ones. This study was a comparative and non-clinical analysis. The population were limited to students in Tehran. A total of 448 students were recruited as a sample using a convenience sampling method. They were also screened using a DASS Test comprising of 21 items. 30 people were depressed, 27 had anxiety and 15 were suffering from stress. Subsequently, 50 people were matched with them. Then both groups were compared using the Stroop test, Wisconsin Card Sorting and a cognitive ability test. Using MANOVA test, data analysis revealed that there are no significant differences among four groups in selective attention and shifting attention. Depressed group reacted rapidly as opposed to the anxiety group in measures of shifting attention and in cognitive abilities; it was observed that the memory, inhibition control, planning, and flexibility of the healthy group were better than those of the three groups.

Key words: executive functions, selective attention, shifting attention, sustained attention, depression.

Introduction:

Today, there exist a bulk of theories with regard to the related definitions of cognitive processes and suitable methods in order to measure executive functions (Wood, 2013). Welsh and Pennington (1988) defined executive functions as being a solution for obtains future targets. They specified four key elements of intention/target orientation, inhibition, planning and working memory for these executive functions. Miyake, Friedman, Emerson Witzki, Howerter and Wager (2000) introduced various theories‌ concerning executive functions including the three dimensions of attention shifting, updating the working memory and response inhibition. In general, executive functions can be seen as representing cognitive processes such as the ability to sustain and shift attention, dominant response inhibition, and maintenance of information in the working memory and planned responses (Pennington and Ozonoff, 1996). Many studies suggested that depression is associated with an impairment of executive functions (Alves, Yamamoto, arias-Carrion, Rocha, Nardi, Machado and Siva, 2014, Otte et al, 2015) and people with depression appear worse in comparison to healthy people in executive function tests (Doumas, Smolders, Branfaut, Boukaert and Krampe, 2012). It seems that marked dysfunction in frontal regions of depression persons is associated with impaired executive function in these patients (Alves et al, 2014). Review of the research literature concerning the study of the relationship between depression and executive dysfunction brings about controversial results. Some studies have found that depression is associated with deficiencies in executive functions (for instance, Brooks, Iverson, Sherman and Roberge, 2010, Dulay, Busch, Chapin, Jehi and Najm, 2012, Vergara-Lopez et al, 2013, Wagner, Alooy and Abramson, 2015). However, other studies did not observe these deficiencies and impairments in depressed people (Watkins and Brown, 2002; Smitheman, Huerkamp, Miller, Houle and O’Jile, 2007, Holler, Kavanaugh and Cook, 2013, Fujii et al, 2013). Based on such controversy, it seems that the intensity of the deficiency in executive functions depends upon the intensity of depression (Bredemier, 2012, Holler et al, 2013). In spite of a strong relationship between depression and anxiety, little attention has been given to the relationship between the executive functions and anxiety. It can generally be stated that the studies carried out in this area have no specific experimental framework utilized in evaluating executive functions in cases of anxiety. In consequent studies concerning these kinds of cases, mixed results have been obtained (Vadnais, Behm, Laake, Lopez, Oddi, Wu & Bridgett, 2013). For example, Billingsley -Marshall et al (2013) and Visa-Petra, Miclea and Visa-Petra (2013) found that people with high levels of anxiety have deficits in their executive function. However, Smitheman Huerkamp, Miller, Houle and O`jile (2007) and Fuji et al (2013) could not find a relationship between self-reported anxiety symptoms and impairment of executive function. It seems that the degree of executive function deficit is related to the intensity of anxiety symptoms (Bredemeier, 2012). Executive functions are possibly susceptible to impairment by stress (Blair et al, 2011). It is suggested that the relative capacity of executive functions can predict the presence of anxiety. Previous studies have not yet clarified the relationship between the executive functions and stress (Hendrawan, Yamakawa, Kimura, Murakami and Ohira, 2012). In this respect, some studies found that high levels of stress are associated with low levels of executive function (for example, Blair et al, 2011, Hendrawan et al, 2012). However, Wudarczyk (2010) found that when people are faced with stress before a task, the executive functions are not affected. Due to the inconsistencies in previous research, further studies on executive functions and depression, anxiety, and stress are required. In addition, no studies have so far been found comparing the three disorders together as well as comparing these groups with healthy people and in non-clinical subjects. Accordingly, the research question is raised as how executive functions are formed in students with depression, anxiety and stress symptoms.

Method

Participants

This is a comparative cross sectional and non-clinical study. The sample population studied comprises the entire student body of the Shahid Beheshti University in Tehran, Iran from which 448 students (female and male) were selected. The subjects were selected using convenience sampling.

Amongst the research population (448 students) , tests of DASS which had 21 questions to allow screening uncovered 30 depressed students, 27 anxious ones and 15 having stress  (cut off point for depression test: 14, anxiety test: 10 and stress test: 19). The rest were healthy students that among them 50 students were matched in terms of gender, age, marital status and occupations with test groups as a control.

The mean age of the sample group was 22.61 years old (standard deviation 2.5). It should be noted that 30 individuals were males and 92 ones were females.

All groups were tested using a Stroop test, Wisconsin Card Sorting Test and questionnaires concerning comparison of cognitive abilities.

The most important moral principles taken into consideration in the present study were as follows:

- Getting consent from the participants before doing the research. All students had a right to privacy when participating in research. Also we are sure about the participants’ rights during the research.

-This study was approved by Research Ethics Board (REB) of Shahid Beheshti University for the ethical and regulatory compliance of research involving human subjects. We are committed to protecting the rights and welfare of subjects enrolled in research activities.

Material

Demographical features questionnaire:

A researcher-made questionnaire was used to determine the features of subjects’ demographics including age, gender, education and marital status.

Depression, Anxiety and Stress Scale (DASS)

This scale was produced by Lavibond and Lavibond in 1995; it is a collection of three self-reporting scales for measuring the intensity of depression, anxiety and stress symptoms within one week. Every sub-scale encompasses 7 items being scored from 0 (meaning this is not true about me) to 3 (meaning this is true about me). Since, this form of the questionnaire (21 questions) is a shorter form of the larger scale (42 questions), the final score of every sub-scale should be two-folded and then it has to be defined by the use of categorization score table to determine the severity of symptoms (Lavibond and Lavibon 1995). Antony, Bieling, Cox, Enns and Swinson (1998) produced a factorial analysis of the scale and found that about 98% of the variance of the whole scale is due to these three factors. The special values of the stress, depression and anxiety factors of this research are 9.07, 2.89 and 1.23, respectively; and the alpha coefficients are 0.97, 0.92 and 0.95 for these factors. Also, the correlation coefficient between depression and stress is 0.48, anxiety and stress is 0.53 and anxiety and depression is 0.28. In the research by Samani and Jokar (2007), the reliability of the test-retest for depression, anxiety and stress is 0.80, 0.76 and 0.77, respectively and the Cronbach alpha is 0.81, 0.74 and 0.78.

Stroop Test:

This test is one of the most applicable tests for the measurement of selective attention and response inhibition (Chan, Chen & Law, 2006; Bozikas, Kosmidis, Kiosseoglou & Karavatos, 2006). In this study, a computer-based version was run which included three stages. The first step tests cohesive struggles, the names of four colors written in black appear in the center of the monitor and the participant has to rapidly press one of the keys representing the colors. In the second stage, the names of four colors appear in the center of the monitor written in their own colors. The participant should then press a key on the keyboard denoting this color. The third step is related to intervention struggles, the names of four colors appear on the monitor in a different color to the one they spell. The participant has to press the color of the font instead of the word. The indices measured in this test are the following: Accuracy (number of correct responses) and speed (mean time of correct responses reaction in versus of stimulant per thousand seconds). The reliability of the Stroop test was reported based on Otello and Graf (1995, cited in Karimi Ali Abadi, Kafi and Farahi 2010), in a test-retesting method for every three tasks was as follows, 0.01, 0.83 and 0.90, respectively. Ghadiri, Jazayeri, Ashayeri and Ghazi Tabatabaiee (2006) reported the reliability of test-retesting of the three tasks as being, 0.6, 0.83 and 0.97. Penner, Kobel, Stöcklin, Weber, Opwis and Calabrese (2012) compared the performance in the original task with computerized version in children and adult. All two versions showed high test-retest reliability and are able to elicit interference effects.

Wisconsin Card Sorting Test (WCST)

This test is a very common test to evaluate executive functions (Rossi, Arduini, Danelluzzo, Bustini, Prosperini and Stratta, 2000).This test is also applied in examining the executive functions of brain such as attention shifting (Sergeant, Geurts and Oosterlaan, 2002), flexibility (Tabares-Seisdedos, Balanza-Martinez, Salazar-Fraile, Selva-Vera, Leal-Sercos and Gomez-Beneyto, 2003) problem-solving (Silverstein, Lefteros and Turnball, 2003) and the concept of the formation and ability to overcome or to persevere (Chan et al, 2006). In this test, the participant should keep a concept or principle received in the test step at frequent cycles and when the principles of sorting change, the early concepts would change in this regard (Ghasemzadeh, KaramGhadiri, Sharifi, Norouzian, Mojtabaei and Raminea Ebrahimkhani 2005). In this study, a computerized version of the Wisconsin test was utilized. This test has 64 different cards, on which there are diagrams of a triangle, star, cross or a circle as well as a number from 1 to 4. Moreover, these cards are colored blue, red, yellow, and green. Hence, the cards have a figure (one of four types), a number (from 1-4), and a color (blue, red, yellow or green). The combination of these gives 64 variations. In fact, every card represents a unique design which is not repeated in any other cards. The scores of the test are as follows: 1-Number of the correct response, 2-Score of perseveration error: this error occurs when the respondent continues sorting based on former principle or a wrong guess, or despite receiving feedback from the assessor trying to avert the incorrect response. 3- Number of clusters: it refers to correct sorting based on three main colors, figure and number ranging from 0 to 3 fluctuating in this regard. The validity of this test is above 0.86 for measuring cognitive deficiencies after traumatic brain events (Lezak, 2004) and its reliability in the research carried out by Spreen & Strauss (1991, cited in Karimi Ali Abad et al, 2010) was reported as 0.83 based on the agreement coefficient of assessors. Naderi (1994, cited in Karimi Ali Abad et al, 2010) reported the reliability of the test using test-retesting method as being 0.85.

Cognitive Abilities Test

This test was created by Nejati (2013); this is a questionnaire including 30 items saturated by 7 factors. Each of these factors have at least three options based on the Likert scale of five multiple-choices ranging from 1 (never) to 5 (always). The reliability of the questionnaire was 0.834 using Cronbach alpha coefficient test. In studying the reliability of the questionnaire via a test-retesting method, the Pearson correlation coefficient was obtained as 0.865 at a 0.0001 level of significance.  

Statistical Analysis

In order to compare the functions of selective attention, Stroop test was applied. To investigate the function of shifting attention WCST was utilized. Moreover, the related test was run to measure the cognitive abilities of the participants. In addition to descriptive indicators of the study variables, to analyze the data obtained and compare the scores of the four groups in each of the instruments, multivariate ANOVA and Tukey post hoc test were used. We performed a power analysis for MANOVA test (4 groups). The results of power analysis showed that there was a  sufficient number of participants (power estimated more than .8).

Findings

Demographic parameters of the participants are given in Table 1.

Table1: Demographic parameters

Stroop test was used to compare the selective attention functions and the scores of four groups were compared using MANOVA in this case. The results are given in Table 2.

Table 2: MANOVA to compare the selective attention functions (Stroop Test) among the groups

As is shown in Table 2, the four groups do not have significant differences in terms of their mean score of correct responses (accuracy) and their reaction time (speed) in any step of the Stroop test (P<0.05).

The shifting of attention functions were studied utilizing Wisconsin test. In order to evaluate the scores of the four groups, the results of MANOVA are given in Table 3.

Table 3: MANOVA to compare the shifting attention (Wisconsin Test) in groups

According to Table 3, there are no significant differences among all groups.

Table 4: MANOVA to compare the Cognitive Abilities Test among groups

According to Table 4, there is a significant difference in all cognitive elements except for social cognition (P<0.05). Tukey test was used to study the differences among the groups; the results are given in Table 5, below.

Table 5: Tukey Test to study the groups’ differences

As is shown in Table 5, there are significant differences between elements of the memory, inhibition control, planning and flexibility of three groups and the healthy group. The memory, inhibition control, planning and flexibility of the healthy group are better in comparison to other groups. Moreover, there is no difference found between the various elements within the three disease groups. In the decision making element, there is a significant difference among the healthy group and the anxiety and stress groups. There is also a difference among the depressed and the anxiety groups in comparison to the stress group. The decision-making of the healthy group is better than the anxiety and the stress groups. Equally, the decision-making of the depressed and the anxiety groups is better than the stress group. In the tests of sustained attention, there is a significant difference among the healthy group and the anxiety sufferers, with healthy people having a better sustained attention.

Discussion

The results of this study substantiated that there were no significant differences among the four groups in selective attention as well as shifting attention. After studying cognitive abilities, it became clear that the memory, inhibition control, planning and flexibility of the healthy group were better than all other groups. Also, the decision-making of the healthy group was better than individuals who suffered from stress and anxiety. The decision-making of the depressed and anxiety groups was better than the stress group as well. In addition, the sustained attention of healthy people was only better than that of anxiety individuals.

 The results showed that there were no differences in selective attention in students of the study groups. This finding is consistent with that of the study conducted by Mogg, Bradly, Bono and Painter (1997). They postulated that attentional bias for threat does not appear in non-clinical anxiety. However, it is inconsistent with Ellenbogen, schwartzman, Stewart and Walker (2002) on impairment of selective attention under stress statues and with the study by Wells and Beevers (2010) about deficits of selective attention in individuals with depressive symptoms.

The finding of this study about differences among groups in shifting attention is not in line with the results of Bredemeier (2012) which indicated that the shifting attention of depressed people is worse than people with anxiety. Also inconsistent with Vergara-Lopez et al (2013), it showed that inhibition of attention shifting was related to depression and anxiety. But in the studies of Watkins and Brown (2002), Smitheman et al (2007), Holler et al (2013) and Fouji et al (2013) such impairments were not observed in depressed people.

Also, there are not differences among depressed and healthy groups in sustain attention. This finding is inconsistent with the study carried out by Wagner et al (2015). They predicted that sustained attention in depressed individuals was worse than that in healthy ones.

Also, this study showed that the depressed group was worse than healthy people in terms of the measures of memory, inhibition control, planning and flexibility. This conclusion is concordant with the research of Brooks, Iverson, Sherman & Roberge (2010) and Dulay et al (2012) but it does not agree with the findings of Smitman et al (2007), Fuji et al (2013) and Watkins and Brown (2002). Moreover, both groups suffering from anxiety and stress have worse measures of decision making affairs in comparison with the healthy group. This finding is in agreement with the results of Bilingsli-Marshal et al (2013) and Visa-Petra et al (2013); however, it is not in agreement with the research by Smitheman et al (2007), Fuji et al (2013) and Watkins & Brown (2002). In addition, anxiety and stress groups are worse than the healthy group both in the above components and in the decision-making. This finding concerning anxious people is consistent with the research by Billingsley-Marshall et al (2013) but is in disagreement with the research by Smitheman et al (2007) and Fuji et al (2013). Concerning people with stress, this study is consistent with that of Blair et al (2011) and Hendrawan et al (2012) but is not in agreement with Wudarczyk (2010). It may pertain to the fact that lack of a difference among the depressed, anxious and stressed people in comparison to healthy people, in the other executive elements, are related to the intensity of symptoms. These elements include the selective and sustained attentions (except for anxiety group in sustained attention). A bulk studies that observed a difference among one of these three disease groups and healthy people carried out tests on individuals with up to moderate symptoms while in this study the symptoms of the population was below moderate at three groups. In this research, the process of decision-making in the three groups is worse than that in the healthy individuals. This result is consistent with the study of Anderson, Arnold, Angus & Bryce (2009) which assessed the impact of depression and anxiety on the process of decision making and the research carried out by Stracke, Polzer, Wolf and Brand (2011) which looked at stress. In addition, amongst the three groups with related symptoms, the decision making of stressed people was worse than both depressed and anxiety groups. This was probably due to the disruption of decision making in people with depression and anxiety, the only dysfunction happens in emotions (Paulus and Yu, 2012) but the stress and decision making are complexly related to each other not only in behavioral level but also in neural level since the brain areas related to the decision making are susceptible to changes-induced stress (Stracke and Brand, 2012). The final point in the present study for discussion was the fact that people with anxiety sustained their attention worse than healthy people. This finding is consistent with the research conducted by Ballard (1998) based on the negative impact of anxiety on sustained attention. However, it is not consistent with the research by Arjmandi Beghlar, Zarenezhad Ashkzari, Nejati, Shah Mansouri and Raoufi Ahmad (2013). This might be due to the differences of the sample population because they carried out their research on cardiac patients within the clinical environment whilst the present study was carried out on students. In general, sustained attention is related to the maintenance of vigilance over time (Bishop, Lau, Shapiro, Carlson, Anderson and Carmody, 2003) and is considered a basic requirement for processing information. Almost, all aspects of cognitive-processing such as encoding, storage, planning and problem solving happen within the periods of sustained attention (Proges, 1980; Richards & Hunter, 1998; cited in Kung et al, 2010). It should be noted that people with deficiencies in sustained attention may not be able to adapt to the demands of the environment, and may not perform well in this setting by inhibiting inappropriate behaviors (DeGangi and Proges 1990; cited in Kung et al, 2010). It is obvious that in maintaining vigilance to threatening stimuli, people with anxiety can lower their sustained attention making operation of other aspects of their executive functions difficult as well as lowering their ability to adapt to their environment demands in this pavement.

Conclusion

 The findings of this research raised specific issues in relation to the role of depression, anxiety and stress in the disruption of the executive functions of sufferers. Selective and shifting attention and cognitive abilities are specifically affected in this regard. Meanwhile, the role of stress in deficits in decision making and the major role of anxiety in deficit of sustained attention was shown to be considerable in this regard. For this reason, all of the students were recommended for suitable treatment. In addition, none of the groups had difficulties in comparison to healthy people in the cognitive neurological tests; however, they showed dysfunction in the questionnaire test; in other words, there was no problem with respect to the executive functions of these people but they may have had these problems from their own viewpoints. Much of these functional deficiencies may come from a lack of confidence or the perfectionism of such people; for that reason, these issues should comprehensively be examined in future studies.

Since all the differences in the prepared research have been gained through cognitive abilities questionnaire and no difference was observed in objective tests, it seems that differences are the result of questionnaire self-reporting bias. In fact, the participants have the mentioned defects in executive functions regarding to their idea while objective tests did not confirm the mentioned differences in any groups. Non-clinical symptoms should also be taken into account as disorders in executive functions of depressed and restless individuals gained through clinical samples in most of the previous researches. A dearth of research on non-clinical samples is clearly seen in this field. Accordingly, related subjects are recommended for future studies.

Acknowledgments

We would like to thank all involved students for their participation. Moreover, we are very grateful to a reviewer for the most valuable comments and helpful suggestions, which improved the article substantially. The study was supported by a grant from Shahid Beheshti University, Tehran, Iran.

The authors declare no conflict of interest.

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