Assessing the Relationship between Personality Traits and Clinical Aspects in Individuals with Multiple Sclerosis

Abstract

Personality traits significantly impact chronic diseases, affecting disease management, coping strategies, psychological well-being, and overall quality of life. People with Multiple Sclerosis (MS) often exhibit dysfunctional personality traits associated with negative disease outcomes, including personality changes and disorders. Our study explored personality traits and their connection to clinical aspects and cognitive functioning in MS patients. We used two assessment tools: the NEO-FFI and the Lüscher Color Test, which is based on color preferences. The aim was to investigate the applicability of the Lüscher Color Test in MS patients. The study included 20 participants from the Swiss Multiple Sclerosis Cohort. The results showed elevated scores in neuroticism, openness, agreeableness, and conscientiousness in MS patients, while there was no effect for extraversion. A significant positive correlation was found between neuroticism and the preference for green-blue color shades, as well as a rejection of orange-reddish color shades in the Lüscher Color Test, indicating avoidance of stimulation and engagement. Another notable positive association was found between openness and the preference for lighter shades in the Lüscher Color Test. Although this relation did not reach the level of statistical significance, it suggests a potential trend. Neuroticism on its own predicted anxiety and fatigue, while the preference for lighter shades in the Lüscher Color Test correlated with EDSS scores. No significant correlations were found between personality traits and cognitive aspects. Despite the limitations of this study, our results highlight the importance of assessing personality traits in MS patients, using either the NEO-FFI or the Lüscher Color Test, to improve treatment strategies and explore emotional conflicts related to the disease.

1. Introduction—Personality in MS Patients

Multiple Sclerosis (MS) is the number one cause of non-traumatic neurological disability among young adults with evidence for increasing incidence and prevalence worldwide [1,2]. This chronic inflammatory disease is characterized by demyelination and axonal degeneration within the central nervous system [3]. Neural lesions and atrophy can be found in all parts of the CNS but seem to appear most in the white matter of the cerebral hemispheres, the optic nerve, the cerebellum, the brain stem, and the spinal cord [2]. The broad variety of affected regions also manifests in a wide range of clinical symptoms, such as physical impairments, cognitive deficits, and psychological changes, resulting in heterogeneous and individual disease courses [4].

MS is a multifaceted autoimmune disorder characterized by the involvement of various immune cell populations, notably T lymphocytes and B lymphocytes [3]. Despite extensive research, the exact cause still remains uncertain to this day. It is generally known that complex genetic and environmental interactions play a significant role in the development of the disease. For instance, individuals who develop an EBV infection in adolescence who are also HLA-DRB1*15:01-positive are at a fivefold increased risk of developing MS [2,3]. Researchers have identified several factors that may add to the multifactorial causes of MS. These include insufficient vitamin D levels, exposure to ultraviolet Blight (UVB), Epstein–Barr virus (EBV) infection, obesity during adolescence, and smoking, among others [2]. However, while these factors are linked to a higher risk of developing MS, they do not offer a complete understanding of the disease’s etiology.

In order to gain a more comprehensive insight into the disease as a whole, there has been a noticeable shift towards a broader range of perspectives in recent decades. While traditional research primarily focused on neurological and cognitive aspects, there is now a growing interest in considering psychological factors, such as personality traits.

Personality is often referred to and defined as a pattern of thoughts, feelings, and behaviors unique to a person. Moreover, personality traits are relatively stable characteristics that persist over time and across various situations. Based on this concept, assessments serve as tools for making individual differences visible, reliably predicting behavior, and determining the consistency of an individual’s behavior over time [5]. One of the most popular, empirically supported, and scientifically used personality taxonomies is the Five Factor Model (FFM) [6,7,8,9]. It is known to describe the fundamental structure of human personality by distinguishing the following five core traits: Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness [8].

In general, personality traits have often been found to be crucial variables in the context of chronic diseases since they have long been known to contribute to disease states and disease progression. More specifically, research indicates the importance of personality traits when explaining individual differences in disease acceptance, coping styles, psychological well-being, and overall quality of life [10,11]. In addition, disease management seems to be influenced by personality traits [11,12,13].

Only limited research concerning the effects of personality traits on individuals with MS is available. However, the available studies based on the Five Factor Model commonly suggest that MS patients show lower levels of extraversion and higher levels of neuroticism than healthy persons [12,14,15,16,17]. Some researchers have also reported reduced levels of conscientiousness and agreeableness among people with MS [16,17,18,19]. Comprehensive reviews consistently point out that personality traits commonly observed in people with MS are often dysfunctional and can negatively impact many disease outcomes [16,20]. In particular, there is a higher incidence and prevalence of personality changes and personality disorders in individuals with MS [9,15,21,22] and elevated levels of neuroticism in MS have been found to be associated with greater disability [15], as well as increased somatization and pain [10] and more mental health problems, particularly anxiety and depression [10,15,21,23].

This is also linked to the observation that high levels of neuroticism in those affected by MS are often associated with the use of emotion-focused coping strategies and avoidant coping mechanisms, indicating a tendency to withdraw or avoid stressors [12,13,16,24]. In addition, MS patients with elevated neuroticism levels appear to have poorer disease management and treatment adherence than less neurotic patients [10,23,24,25]. Finally, some researchers have also shown a link between neuroticism and cognitive deficits, particularly in the memory domain [17,26].

Apart from these relatively consensual findings, further research is needed on several other aspects of the illness as some relationships between neuroticism and disease outcomes have been shown to be complex. For example, while several explorations suggest a plausible link between neuroticism and fatigue in MS patients [16,27,28], this association seems to disappear in a number of studies after controlling for depression [29,30].

In contrast to neuroticism, extraversion seems to have a rather mixed impact on individuals with MS according to the available studies. On one hand, lower levels of extraversion have been associated with fatigue by various researchers. However, similar to neuroticism, these effects seem to diminish in some studies when depression is taken into account [28,29,30]. On the other hand, increased levels of extraversion have also demonstrated beneficial associations with disease outcomes. For instance, they have been linked to milder disability levels [15] and the preservation of subjective well-being [31]. Moreover, research has indicated correlations between higher extraversion and positive attitudes, as well as effective planning and activity strategies [13].

When extraversion is considered together with conscientiousness in MS patients, it serves as a predictor of effective self-management, increasing the likelihood of proper disease management [25]. These two personality traits have also been found to be related to greater engagement coping in meta-analysis [12] and to problem-centered coping [16] in general. Nonetheless, extraversion and conscientiousness have been shown to decline in individuals with MS over the course of 5 years, especially when cognitive skills decline as well [17]. This once again highlights the complex intercorrelations of personality traits with other disease-related outcomes, which in this case is cognitive deterioration.

Regarding future employment status, conscientiousness emerges as an important trait [19]. By itself, low conscientiousness not only predicts adverse patient outcomes in general but also heightens the risk of mood or anxiety disorders, potentially impacting the cognitive function of MS patients [17]. Moreover, conscientiousness has been found to decrease longitudinally in individuals with MS, exacerbating these problems [17,32]. Conversely, high conscientiousness levels in MS patients have been linked to greater treatment adherence, enhanced rehabilitation outcomes [19], better self-assessment, and even a lower risk of mortality [10].

Additionally, heightened levels of openness have been associated with increased engagement in diverse, stimulating activities, which can benefit and protect cognition [16,33].

Besides the Five Factor Model, there are also various other theories and methods to assess personality. One of these alternative approaches is used by the Lüscher Color Test, which was developed by the Swiss psychologist Max Lüscher [34] and claims to represent a non-projective, non-verbal, and multidimensional personality assessment tool. The test is based on a dimensional theory of emotions, developed by Max Lüscher at the University of Basel in the late 1940s, and shares similarities with the “three-dimensional theory of emotions” by Wilhelm Wundt, one of the founders of experimental psychology [35]. This theory postulates that human emotions result from the fusion of a characteristic ‘mixture’ of six basic forms of feeling: pleasure, displeasure, excitement, inhibition (tranquillization), tension, and relaxation. These basic feeling types are organized into three bipolar dimensions, and the basic feelings experienced toward complex objects are a fusion of the corresponding basic feelings directed at the components of the complex objects. The bipolar dimensional relationship can be represented by an axial system. Within this context, he also studied the ability of colors to elicit different emotional values (e.g., the contrast between red eliciting an exciting effect and blue having a calming effect). Later on, this pioneering work was refined by Max Lüscher, who, based on these findings, then used colors as an instrument for objectifying crucial “self-feelings”, such as belonging (attachment), self-esteem, self-confidence, and freedom, which are governed by emotions as a regulatory entity along a four-dimensional space. Accordingly, the test colors follow this system, by using an individual’s color selection to reveal which feelings are avoided, which are preferred as corresponding compensation, and for what purpose they are pursued in order to explore pertinent emotional states and tendencies [36]. Since this approach is based solely on color preferences, it avoids semantic-associative top-down processes induced by questionnaire-based personality inventories using a variety of statements about thoughts, feelings, and goals, thus eliciting cognitively biased responses.

This test is based on the principle that the appearance of colors is objective for human perception [37], whereas the emotional preference for colors represents the subjective component, reflecting the fourth emotional dimension of sympathy versus antipathy in Lüscher’s model of emotional theory.

The colors that have been specifically designed for the Lüscher Test are assumed to trigger similar physical responses and are perceived in a comparable and objective way by people across different cultures. For example, orange-red is perceived as stimulating and invigorating and thus as “active”, in contrast to the calming effect of dark blue, which is perceived as “passive”. This assumption has been further corroborated by recent neurovisual findings showing a lack of variability in categorizing colors between subjects, hence pointing to a universal computational mechanism being adopted by different subjects to perceive colors [37].

The examiner asks a person to evaluate 23 different test colors and seven different shapes, specifically arranged in eight test subsets, in the sense of how colors and forms are specifically experienced (i.e., positive or negative) by asking, “which of these colors do you prefer most”, ”which one do you like second most”, etc., and ”which of these colors do you prefer least”.

By evaluating different colors and different test forms according to individual preferences and rejections, a subject unconsciously reveals his or her individual personal attitude towards a background of six different color-based categories of self-experience, i.e., “directive or receptive”, “constant or variable”, or “integrative or separative”. Based on those predefined categorial structures representing behavioral and motivational aspects of personality, the individual choice and rejection of specific colors therefore enables the delineation of an individual personality profile. As stated above and contrary to test items commonly employed in questionnaire-based personality inventories, the preference-based color choice follows a non-cognitive approach, free of semantic associative loads. Hence, it is assumed that based on this individual color selection profile, either emotional balances or disbalances such as tensions, aversions, etc., can be expressed without a top-down bias [34,38,39,40]. This approach has recently shown promising results in different clinical fields [40,41,42].

Furthermore, given that the test material is based on a non-verbal preference paradigm, its administration is economical and easily applicable in clinical settings. As of now, there have been no published studies on the application of the Lüscher Color Test in MS patients.

However, the role of personality and its importance in the context of MS becomes particularly clear when considering its correlations with various named aspects, contributing to the overall burden of the disease and quality of life [31]. As the current research indicates, understanding the associations between personality and MS is vital for optimizing disease treatment and potentially influencing disease progression. The relevance of personality in the context of MS becomes even more apparent when explaining individual differences between patients. Moreover, it contributes to the ongoing refinement of our knowledge about the disease, helping us to gain a more comprehensive understanding of this neurological condition and providing valuable insights for potential interventions and personalized healthcare strategies.

2. Aim of the Study

Our study aims to explore the personality traits of individuals with MS in order to depict a characteristic personality profile based on the outcomes obtained from two distinct personality assessment tools, namely the NEO-FFI personality test and the Lüscher Color Test. By analyzing the intersections and patterns shared by these two different personality test approaches, we seek to provide a comprehensive view of the personality traits in individuals with MS. Our primary focus was to assess the applicability of the Lüscher Color Test in the context of MS patients and to determine whether the tests could serve as an effective alternative in clinical settings, given their efficiency and the low cognitive load required by the sole preference of colors.

According to the given research, we hypothesized that people with MS show higher levels of neuroticism and lower levels of extraversion. Furthermore, we expected that these personality traits also correlate with the patients’ clinical outcomes, such as disability severity, anxiety, and depression, as well as cognitive impairments. Therefore, our secondary goal was to investigate the relationship between the shared outcomes of the personality tests and cognitive functions, along with various clinical aspects.

Furthermore, and based on the aforementioned theoretical background, we expected that individuals with higher scores in neuroticism might demonstrate an increased tendency towards emotional conflicts, as represented by specific color preferences in the Lüscher Color Test. These expectations were driven by the resemblance between the measurement constructs used in the Lüscher Color Test and the characteristics associated with neuroticism.

3. Method

A total of n = 20 patients were recruited from an ongoing local MS cohort in the MS center at the University Hospital of Basel. The inclusion criteria were: (i) age ≥ 18 years old, (ii) eligibility for a color-based psychometric test (i.e., ability to fixate with each eye), and (iii) sufficient proficiency in the German language. The exclusion criterion was: (i) serious ophthalmological comorbidity, such as glaucoma or other retinal pathology that could interfere with color perception). Every patient who was enrolled in the research cohort project from February to August 2023 was given the possibility to participate in this study.

This study was conducted in accordance with the Declaration of Helsinki and released by the local ethics committee (Ethikkommission Nordwest- und Zentralschweiz, EKNZ 48/12), Basel, Switzerland (PB_2016-01171). Participants were asked to take part in a study concerning personality traits of people with MS and gave written consent. The examinations were conducted by a trained research assistant at the University Hospital of Basel between February and August 2023. Participants were on average 44.75 years old (SD = 11.45 years, range = 30–71 years) and had 14.33 years of education (SD = 3.13 years). The majority of the sample were women (n = 15, 75%). All subjects enrolled in the study had a clinically confirmed diagnosis of MS according to the McDonald criteria [43,44]. Out of 20 patients, 18 patients (90%) had a relapsing-remitting disease course, while one person had a secondary progressive course and another person displayed a primary progressive disease course. The mean EDSS (Expanded Disability Status Scale [43]) score was 2.65 (SD = 1.75, range = 0–7) and mean disease duration was 14.65 years (SD = 9.06 years). At the time of data collection, 18 individuals (90%) were being treated with disease-modifying therapies and for all patients, there was a minimum six-month interval between the most recent relapse and data acquisition. The main sociodemographic and clinical values are shown in

Table 1. Sociodemographic and clinical characteristics of participants.

Characteristic	Mean	SD
Age at test	44.75	11.45
Years of education	14.32	3.13
Disease duration	14.65	9.06
EDSS a	2.65	1.75

Note. ^a Expanded Disability Status Scale. n = 20.

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4. Personality

Personality traits were investigated with the NEO-Five Factor Inventory (NEO-FFI), which is based on Costa and McCrae’s Five Factor Model [6,8]. This self-report questionnaire contains 60 items to which participants respond on a five-point Likert scale, ranging from 1 (strongly disagree) to 5 (strongly agree). Each core personality trait (Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness) is represented by 12 subscale items. Higher scores indicate a more pronounced expression of the respective trait, e.g., a higher level of openness. Raw scores were converted into T-scores for each trait domain using combined gender norms reported from the German norm sample [44].

To explore other fundamental aspects of personality, including emotional structure and basic affective states, the Lüscher Color Test [38] was used. The test is based on color preferences with eight independent subtests (T1–T8, shown in Figure 1), in which 23 precisely defined but different colors and seven distinct shapes are presented. There are four basic colors (blue, green, orange-red, and yellow), including different nuances thereof, and four auxiliary colors (magenta, black, gray, and brown), each with a distinct psychological assignment (cf. previous section).

During the test, participants sequentially select colors (T1 and T2) and shapes (T3) by making repetitive preference decisions between color pairs (T4–T8). In this process, participants rank the colors, with the first choice representing their favorite and the last choice indicating their least favorite, thus revealing their attractions and aversions. Through this ranking, the test determines individuals’ emotional states and consistently categorizes them into unique patterns of experience, sensation, and behavior, which are characteristic of each person.

5. Cognitive Functioning

Cognitive performance was assessed by using the following tests.

5.1. Multiple Sklerose Inventarium Cognition (MUSIC)

This cognitive screening test assesses MS patients’ most frequently impaired cognitive areas, such as verbal memory, verbal interference susceptibility, verbal fluidity, mental “set-shifting”, information processing speed, inhibition, and long-term memory. Additionally, it also contains a fatigue scale, screening for physical, social, and mental fatigue [45].

5.2. Verbal Learning and Memory Test (VLMT)

The VLMT evaluates verbal, short-term, and working memory by measuring an individual’s ability to learn and recall a list of 15 words [46].

5.3. Trail Making Test A and B (TMT A and B)

These tests measure visual attention, mental flexibility, and processing speed. TMT A focuses on simple visual tracking, while TMT B incorporates task-switching and complex executive functions [46].

5.4. Symbol Digit Modalities Test (SDMT)

The SDMT [47] assesses processing speed and attention by requiring individuals to match symbols to corresponding numbers under restricted time conditions, making it useful for detecting impairments in mental speed and flexibility.

5.5. Rey–Osterrieth Complex Figure Test (ROCFT)

This test mainly measures visuospatial memory by asking individuals to copy and later on reproduce a complex geometric figure from memory [46].

5.6. Stroop Test

The Stroop Test requires the individual to name the color in which words are written while disregarding the word’s actual meaning in different conditions (congruent or incongruent color/word/meaning) and evaluates cognitive flexibility, processing speed, and inhibitory control [46].

5.7. Digit Backwards Span

This test evaluates working memory capacity by requiring individuals to repeat a series of numbers in reverse order, assessing their ability to temporarily hold and manipulate information in their short-term memory.

5.8. Oral Trail Making Test (oTMT)

As the nonmotor and nonvisual version of the TMT, the Oral Trail Making Test serves as a tool for evaluating sequential set-shifting abilities without the influence of visual and motor factors. Therefore, this test is especially useful for assessing patients with impaired vision or motor skills, which are frequently presented in MS patients.

6. Clinical Measures

Clinical parameters were assessed using the following measurements.

6.1. Expanded Disability Status Scale (EDSS)

Physical disability was measured using the EDDS score [48]. It serves as an indicator of the patient’s disease progression and neurological impairment. In each case, the score was determined by the patient’s treating neurologist at the time of enrollment.

6.2. Hospital Anxiety and Depression Scale (HADS)

The HADS [49] is a self-assessment tool that measures the severity of anxiety and depression symptoms in patients with physical illnesses or complaints. The questionnaire has been validated to serve as a reliable indicator for detecting major depression and generalized anxiety disorder among MS patients [18].

6.3. Fatigue Scale for Motor and Cognitive Functions (FSMC)

The FSMC [29] is a diagnostic tool designed specifically for individuals with MS and measures the impact of fatigue on both motor and cognitive functions, offering a comprehensive assessment of disease-related fatigue.

7. Coding and Statistical Methods

To analyze the Lüscher Color Test results, we first transformed the raw scores into a format suitable for statistical analysis. We followed the guidelines of the Lüscher Diagnostic Manual [38] to identify values that stood out and then recoded and reordered the frequently chosen color preferences and rejections from the pairwise choices. This allowed us to create an ordinal scale, ranging from most preferred to least preferred or neutral color shades. As for the basic and auxiliary color choices, we assigned a corresponding number to each color and recorded them in a nominal variable. In cases where there was no preference or rejection, we coded it as 0.

Regarding cognitive performance, we sought to consolidate and combine all the measured variables into a single comprehensive measure of cognition. To do so, we used a random forest model to handle missing data in our dataset. Following that, we conducted a factor analysis to identify an underlying latent variable known as the “g-value” for cognitive performance.

The relationship between the personality variables was assessed through Spearman’s Rho correlation coefficient. When our analyses revealed statistically significant results, we further explored these associations by conducting multiple regression analyses.

In considering the independent variables, a sequential variable introduction and “step down” approach was adopted. Besides group, demographics and neuropsychological variables were considered as covariates.

These analyses aimed to examine how the common personality outcomes might be related to additional clinical or cognitive factors in our study.

When analyzing the various parameters of the Lüscher Color Test, we performed separate calculations for frequency counts and percentages. This allowed us to identify exaggerated patterns in the selection of colors which—according to the manual—indicate the presence of emotional conflicts. When there were no preferences or notable attributes detected, we coded it as a 0.

All statistical analyses were performed using RStudio version 2022.12. Statistical significance was defined as a p-value < 0.05.

8. Results

The factor analysis results revealed that the SS loadings, totaling 15.81, indicate that approximately 42% of the variance in the data is effectively explained by a single factor, referred to as the cognitive performance factor. This finding highlights the ability of the one-factor approach to explain a substantial amount of the variance within the observed cognition variables. In general, the one-factor model shows a reasonable fit to the data, emphasizing its ability to capture the underlying structure.

Regarding the NEO-FFI, the subjects of our study showed significantly higher scores in neuroticism, openness, agreeableness, and conscientiousness compared to the German norm sample [50]. No differences were found between the two samples in regard to the extraversion trait. The results are presented in

Table 2. NEO-FFI T-scores.

Personality Trait	Mean	SD	p-Value
Neuroticism	55.10 *	10.51	0.04
Extraversion	53.24	11.51	0.22
Openness	59.47 *	10.17	<0.01
Agreeableness	55.35 *	8.99	0.02
Conscientiousness	57.27 *	11.38	0.01

Note. * = p < 0.05. n = 20. Normative sample used for comparison: [50].

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For the Lüscher Color Test, we report frequent values in percentages as selected by the participants. A value of 0 means the absence of salient choices, i.e., “emotional conflicts”.

Within the eight-color table, in which the four basic (yellow, orange-red, blueish green, and dark blue) and the four auxiliary (fuchsia, brown, gray, and black) colors are present, more than 50% of the participants exhibited a preference for the auxiliary colors black, gray, and brown (which should be rejected rather than preferred following Lüscher’s emotional-motivational model of personality). The most preferred color (35%) was gray, representing a need for shielding and self-protection against oppressive demands, followed by a preference for brown (15%), representing an increased desire for conflict-free comfort, sensuality, and relaxation. Lastly, 15% of the participants chose black, representing a protest against intolerable conditions that have been experienced.

On the other hand, roughly 80% of the participants were rejecting one or two basic colors in the eight-color table, with red and yellow being about 50% of the rejected basic colors. In this context, the rejection of red symbolizes a defense mechanism against exciting stimuli, as they may be perceived as overwhelming, overstimulating, aggravating, or even threatening. This reaction is often linked to feelings of weakness, resignation, or depression, and a decline in self-confidence. Similarly, the rejection of yellow represents the fear of change and insecurity, which is grounded in the fear of being lost and losing what is supposed to provide security. The residual (both 15%) rejected basic colors were blueish green, reflecting the avoidance of restrictions and rules, and blue, representing dissatisfaction with the current circumstances.

Within the variation lines, i.e., the specific color selection pattern in tables T4–T8, where colors are presented pairwise, as shown in picture 1, the most frequent (65%) rejection was shade number 3, normally characterizing stimulation, engagement, and excitement; however, its negation suggests that individuals are confronted with overwhelming or stressful circumstances. This rejection also points to overstimulation, leading to fatigue and possible exhaustion. Moreover, it may serve as an indicator of diminished self-confidence with a tendency to become agitated and angry. Furthermore, 30% of the participants showed a rejection of shade number 4, which normally characterizes openness; however, its negation reflects the psychological meaning of anxiousness, insecurity, and disappointment.

Furthermore, within the variation lines, 50% of the participants showed a preference for a separative pattern. This pattern included a preference for the color shades with the numbers 2 and 4, which can be described as a blue-green tint for structure 2 and light shades of the basic colors for structure 4. The separative category for structure 2 implies a self-asserting, defensive attitude demanding authority, competence, and superiority, whereas structure 4 reflects an evasive and distant attitude.

Regarding the gray color plate, which serves as an indicator of the current subjective mood, 75% of the participants expressed a preference for specific gray tones, suggesting a conflict-prone connotation. Black (structure 2) was chosen in 35% of cases, representing persistent self-assertion in a protesting and defensive fashion, and white (structure 4) was chosen in 30% of cases, reflecting a need for liberation from stressful hindrances. In addition, dark gray (structure 1) was chosen in 30% of cases, indicating a need for affective belonging,

On the other hand, the most frequently rejected colors in the gray color plate were medium gray (15%), which typically signals an urge to change circumstances, and dark gray (15%), which conveys a sense of dissatisfaction without a sense of belonging, while 60% indicated no conspicuous and conflict-prone choice.

Correlational analyses were carried out to assess the relationships between the NEO-FFI and the results of the Lüscher Color Test. The personality trait of neuroticism and a specific aspect of the Lüscher Color Test, namely the preference for the green-blue color shades representing the request for self-esteem, respect, and competence, as well as the rejection of structures 3 and 4 in the variation lines, indicating dispositions for depression and anxiety, showed a significant positive correlation (ρ = 0.47, p = 0.04). This finding fits the general picture of elevated incidences of depression and anxiety, which is well-known in MS. In addition, another notable positive association was found between the personality trait openness and the frequency of choosing lighter shades for each color in the Lüscher Color Test (ρ = 0.41, p = 0.07). Although this correlation did not reach the significance level, the results indicate a possible trend. No further interactions were significant.

In our further exploration using multiple regression analysis, we examined the predictive relationships between personality traits and various clinical aspects. The analysis revealed a significant result, where neuroticism together with the preference for green-blue color shades showed the ability to predict anxiety in patients (F(2, 17) = 5.04, p = 0.02, R² = 0.37, R²_Adjusted = 0.30). The overall model explained a considerable amount of the variance in anxiety, accounting for 30%. However, as individual predictors, only Neuroticism significantly influenced anxiety in the model (p = 0.01) and not the preference for the green-blue color shades.

A similar pattern emerged for the interaction between neuroticism, the preference for green-blue color shades, and fatigue. The overall model was statistically significant, explaining 24% of the variance in fatigue (F(2, 17) = 4.04, p = 0.04, R² = 0.32, R²_Adjusted = 0.24). Yet, when considered as individual predictors in the model, only neuroticism significantly influenced fatigue (p = 0.01). In our study, this effect between neuroticism and fatigue remained significant, even after controlling for depression (Neuroticism: p = 0.04; overall model: F(3, 16) = 4.17, p = 0.02, R² = 0.44, R²_Adjusted = 0.33).

In our analysis of the association between openness and the frequency of lighter shades, we found an interaction effect with the EDSS scores. However, only the preference for lighter shades proved to be a significant predictor of the EDSS scores (p = 0.02), as the overall model did not reach statistical significance (F(2, 17) = 3.04, p = 0.07, R² = 0.26, R²_Adjusted = 0.18).

There were no further empirically relevant correlations between personality and other clinical aspects or cognitive performance.

9. Discussion

The main goal of the present study was to offer a comprehensive examination of the personality traits of individuals who have been diagnosed with MS and investigate their relationship with other clinical parameters and cognitive functioning. To do so, a second personality assessment instrument was used in addition to the NEO-FFI, with the aim of investigating the applicability of the Lüscher Color Test in individuals with MS.

Our results from the NEO-FFI revealed that people with MS show increased expressions of several personality traits, including neuroticism, agreeableness, conscientiousness, and openness. These findings are partially in line with previous research, while also presenting some different trends. Consistent with several available studies, we also observed elevated levels of neuroticism in MS patients [15,16]. However, in contrast to certain other studies which detected decreased levels of agreeableness, conscientiousness, and openness [18,19,32], our sample showed elevated levels of these personality traits. Furthermore, contrary to our hypothesis, our findings did not indicate a decrease in extraversion, as frequently shown in other studies [12,14]. Overall, this highlights the need to further investigate and understand the diverse patterns of personality traits in individuals with MS.

The Lüscher Color Test revealed a preference for green-blue and lighter shades in individuals with MS, which seems to have a meaningful impact in understanding personality characteristics. According to Lüscher [34,38], green-blue shades represent a directive, constant, and separative personality pattern. More specifically, people tend to be self-directed, controlled, and constant in their behavior, distancing or setting themselves apart from others and being cautiously observant. Hence, this color choice might reflect a general strategy adopted by individuals affected by a chronic disease, which per se is associated with uncertainty due to its rather unforeseeable course. On the other hand, the preference for lighter shades represents a receptive, variable, and separative pattern. More specifically, people in these categories are described as open, wanting to participate, standing out from others, observant, and noncommittal. In addition, an unusual preference for the auxiliary basic colors gray, black, and brown was observed to a considerable extent, all of which are rejected rather than preferred in a healthy population [51]. This is viewed as a compensating response to the rejection of the basic colors orange-red and/or yellow, indicating the presence of straining, wearing, exhausting, and discomforting conditions that are currently experienced and which are regarded as constituents of depressive and anxious emotional states [38]. An explanation for the elevated findings might be given by the relatively large number of women represented in our sample, which reflects the female preponderance in the distribution of MS; in fact, when looking at personality traits and depression, it turns out that this relationship is moderated by gender. Conscientiousness, extroversion, and agreeableness have been found to correlate negatively with depressive symptoms, while neuroticism and openness are positively associated. Moreover, gender moderates the relationship between personality traits and depressive symptoms [52].

When examining the frequency of preferred or rejected basic colors in the Lüscher Color Test, the emerging emotional conflicts seem to represent some issues pertinent to a chronic disease. These conflicts include coping with stress or overwhelming situations, a fear of change, feelings of exhaustion, and decreased self-confidence. Additionally, these individuals seem to be seeking comfort and belonging, as well as stability and security in the sense of self-protection against burdening and wearing circumstances. In 50% of cases where separative dispositions were observed, they were linked to either depressive or anxious attitudes, thus enhancing the meaning of the corresponding emotional state. It appears that the Lüscher Color Test is capable of detecting several elements that are summarized under neuroticism, such as depression, anxiety, vulnerability, impulsivity, hostility, and self-consciousness. The significant correlation between high levels of neuroticism seen in the NEO-FFI and the high frequency of the preference, rejection, or avoidance patterns within the Lüscher Color Test supports this assumption.

To the best of our knowledge, this is the first clinical study adopting the Lüscher Color Test in a clinical cohort of individuals with Multiple Sclerosis. Hence, as there are currently no published studies in which the Lüscher Color Test has been used to assess people with MS, a direct comparison with other results is not possible. However, some characteristics identified by the Lüscher Color Test are also consistent with personality traits defined in the Five Factor Model. In particular, increased levels of neuroticism are often associated with a range of negative symptoms, such as feelings of insecurity, anxiety, and difficulty coping with stress. These characteristics are consistent with the emotional conflicts found in our study by adopting the Lüscher Color Test. Therefore, it can be concluded that the Lüscher Color Test may be a valuable tool for exploring personality characteristics, especially emotional conflicts, in people with MS. However, further research is needed to confirm this hypothesis.

Regarding the interaction between personality traits and clinical aspects, our results showed that neuroticism is a relevant predictor. Neuroticism as an individual variable could positively predict anxiety as well as fatigue. These findings underline the results from other studies [16,27,28]. Moreover, contrary to other studies that found no effect after controlling for depression [29,30], the effect on fatigue remained significant in our study, even after controlling for depression. We also found a meaningful relation between one of the Lüscher factors, namely the preference for lighter color shades and EDSS scores, which again speaks for the use of the Lüscher Color Test in MS patients. Hence, our results indicate meaningful relationships between personality traits and fatigue, anxiety, and disability severity in MS patients, which is in line with previous research [12,13,23,24,25].

In contrast to other studies [17,26] and our hypothesis, we found no interactions between personality traits and cognitive functioning. This could be due to the aggregation of all our cognitive variables in the factor analysis. Although the factor analysis explained a substantial amount of the variance between variables, substantial information may still have been lost in the process. Moreover, since we used a cognitive screening instrument to assess cognitive capacity, its raw composite score, together with our relatively small sample size, might have obscured some possible associations between cognitive performance and personality aspects. Finally, it has been shown that personality changes are associated with a cognitive decline over time [17]. Hence, our cross-sectional design might have been too insensitive to detect some relevant relationships between cognition and personality. Finally, another effect that might have influenced both cognitive and personality aspects is the time since diagnosis. Although our sample was too small for a stratified analysis, one might speculate that not only cognition might be negatively affected by MS-related progressive brain damage. Personality changes may also be affected due to insufficient recovery processes over time, cumulative lesion loads, and atrophy. For example, it is reported that the behavioral and coping type of personality (Type A vs. Type B) in MS patients is influenced by disease duration [53]. Hence, future studies should consider disease duration as a covariate to elucidate the relationship between personality and MS more thoroughly.

10. Limitations

Nonetheless, it is important to interpret our results with caution, as the present study has several limitations. In particular, power analysis indicated that our sample size was insufficient and that at least 85 participants would be required to achieve a statistically robust analysis, which was not the case in our study; therefore, our conclusions remain preliminary. A larger sample size might have had an impact on the personality traits that are important in the context of MS. In general, given the relatively small sample size, our results might not be fully representative of the entire population of individuals with MS. In addition, our sample predominantly consists of patients with a relapsing-remitting disease course, so our findings may not be generalizable to people with other forms of MS.

Because MS is a disease that progresses over time and personality traits appear to be influenced and changed by the illness, further studies are needed to capture these changes longitudinally, as our study was a cross-sectional analysis. Moreover, the impact of personality traits on clinical and cognitive outcomes may evolve with disease progression. Additionally, it is crucial to emphasize that personality traits in MS may act as both predisposing or predictive factors, as well as moderators throughout the course of the chronic disease. As our study was conducted as a single-point assessment, we could not distinguish between these two functions.

Regarding the Lüscher Color Test, further research with MS patients is needed, as we still lack a comprehensive understanding of the mechanisms underlying color choices. In general, it is essential to keep in mind that this was the first explorative study analyzing the Lüscher Color Test in the context of MS patients.

In addition, we examined a wide range of cognitive variables. While this is also a strength of our study as it provides an in-depth picture of cognitive functioning, some of this differentiated information may have been lost due to the need for factor analysis.

11. Conclusions

The present study explored personality traits in people with MS based on two personality assessment tools, the NEO-FFI and the Lüscher Color Test. It can be concluded that MS patients frequently show high levels of neuroticism and a variety of emotional conflicts. The results for other personality traits such as openness, agreeableness, conscientiousness, and extraversion seem to vary between different studies. Our findings suggest increased scores for agreeableness, conscientiousness, and openness, whereas there were no effects for extraversion. Regarding the applicability of the Lüscher Color Test, it can be concluded that the test has the potential to shed light on emotional conflicts and could be a useful tool to gain insights into the characteristics of MS patients. Additionally, our study underscores the complex interactions between personality traits and other clinical factors, particularly anxiety, fatigue, and disease progression. It can therefore be concluded that it is important to assess personality traits in clinical settings to improve treatment strategies and patients’ overall well-being. Further studies should focus on exploring the underlying mechanisms of personality traits in MS to gain a more comprehensive insight into their relationship with other clinical outcomes.