Introduction

Fibromyalgia (FM) is characterized by widespread pain, fatigue, sleep disturbances, and various comorbidities. Even though the exact etiopathogenesis is still obscure, many factors can contribute to the development of FM. Apart from well-known factors such as genetic predisposition, environmental, neuroendocrine, and immunological background, psychosocial factors may also play a role in FM [1,2,3]. Accordingly, to date, many researchers have examined psychological parameters in FM [2, 4] and a limited number of studies have focused on the personality type among patients with FM [2, 4,5,6].

Type D personality is characterized by a distressed personality pattern, which consists of two personality traits including negative affectivity and social inhibition [7]. Individuals with type D personality are prone to experiencing unfavorable feelings, such as distress, dissatisfaction, irritability, anxiety, and depression. They also have difficulties in expressing their emotions/behaviors in social relationships, which further lead to feelings of insecurity and vulnerability [5]. Determining the presence of type D personality plays an important role in the clinical progression of certain diseases, such as coronary artery disease, hypertension, heart failure, and brain dysfunction. Many studies have demonstrated the negative impact of type D personality on several clinical conditions [7,8,9,10,11]. Nevertheless, the number of studies examining the importance of personality in FM is relatively few [2, 4,5,6].

Self-esteem is based on a balanced view of oneself, and having self-esteem implies a belief and confidence in self-worth, efficacy, strength, and success [12]. Self-esteem is a self-concept affected by one’s underlying disorders and its consequences, and social support [13, 14]. Studies investigating the impact of self-esteem have shown that low self-esteem is associated with higher suicide risk, together with inappropriate behavior, such as excessive alcohol intake and smoking cigarettes [15, 16]. In contrast, high self-esteem can be a double-edged sword, which causes poorer coping with diseases or ignoring or denying depressive symptoms. Accordingly, the type of high self-esteem classified as ‘fragile’ and ‘secure’ can determine the psychological status of individuals [13, 17]. Self-esteem, pertaining to its level and type, is linked to anxiety and depression, which are essential components of FM [18, 19]. Thus, self-esteem status can be regarded as one of the building blocks of FM [20, 21]. However, studies investigating type D personality, self-esteem and psychosomatic status in FM are very scarce. Given the limited number of studies among patients with FM, the present study aimed to evaluate type D personality and self-esteem in patients with FM and to determine the predictors of type D personality among patients with FM.

Materials and methods

Study population and design

Female FM patients aged between 18 and 60 who fulfilled modified 2010 American College of Rheumatology (ACR) for the classification of FM were enrolled in the study [22]. Patients with neurological diseases/disabilities, inflammatory rheumatic conditions, psychological disorders, drug abuse, and personality disorders were excluded. The control group included healthy, age-matched women. Healthy controls were invited to be assessed for eligibility. The individuals were further evaluated in terms of FM and those who did not meet FM criteria were included in the study.

The present cross-sectional study was conducted at a tertiary institution. The local ethics committee of Cukurova University Faculty of Medicine approved the study protocol (Date 5-June-2015, Number 43/6). Written informed consent was obtained from each study participant. In addition, the study was conducted in accordance with the Declaration of Helsinki and within the terms of local legislation.

Clinical assessment

Demographic characteristics of the study population, including age, body mass index (BMI), socio-economic status (education and occupation, marital status, the number of children, the number of participants’ dependents), and disease-associated variables (i.e. disease duration) were recorded.

Psychological status (depression and anxiety) was assessed by the Beck Depression Inventory (BDI) and the Beck Anxiety Inventory (BAI). The BDI consists of 21 items and each item is scored between 0 and 3. The sum score ranges from 0 to 63. Higher scores indicate depressive mood [23, 24]. The BAI is also a 21-item questionnaire in which each item is scored from 0 to 3. Total score ranges from 0 to 63 [25, 26].

Quality of life, functional impairment, and health status of FM patients were evaluated by the Fibromyalgia Impact Questionnaire (FIQ), consisting of 10 items. Each item is scored from 0 to 10 and the total score ranges from 0 to100. Higher scores represent more functional impairment [27, 28].

Self-esteem and psychosomatic status were evaluated by the Rosenberg self-esteem scale (RSES). The RSES is a self-reported questionnaire, consisting of 63 items under 12 sub-dimensions including self-esteem scale (D1), stability of self scale (D2), faith in people scale (D3), sensitivity to criticism scale (D4), depressive affect (D5), daydreaming scale (D6), psychosomatic symptom score (D7), interpersonal treat score (D8), intensity of discussion index (D9), parental interest index (D10), relationship with father score (D11), and psychic isolation (D12). The self-esteem subscale contains 10 items in which each item is evaluated in accordance with four answers, ranging from ‘strongly agree’, ‘agree’, and ‘disagree’ to ‘strongly disagree’. The sum of scores ranges from 0 to 6 where the higher scores represent lower self-respect. Self-esteem is categorized as high (0 − 1), moderate (2 − 4), and low (5 − 6). The psychosomatic symptom score consists of 10 items in which each item is evaluated based on four answers, that are ‘often’, ‘sometimes’, ‘almost never’, and ‘never’. While often and sometimes are scored as 1 point, almost never and never are scored as 0 point. Total scores vary from 0 to 10 where the higher scores indicate higher psychosomatic symptoms. The psychosomatic symptoms are categorized as many (5 or more), medium (3 − 4), and few (2 or less) [29,30,31].

Type D personality was assessed by the type D scale (DS-14). The DS-14 tool includes two subscales evaluating negative affectivity and social inhibition. Each subscale contains seven items, which are rated on a 5-point Likert scale, scored from 0 (false) to 4 (true). Participants are classified as type D personality if they are scored with ≥ 10 on both negative affectivity and social inhibition [7].

Statistical analysis

Statistical analysis was performed using SPSS, version 20.0 (SPSS Inc., Chicago, IL, USA). The socio-demographic variables and clinical data were evaluated by descriptive statistics. Data distribution was checked by Shapiro–Wilk test. Between-group comparison of continuous variables was performed by Mann–Whitney U test. In addition, between-group comparison of categorical variables was done by Pearson’s chi-squared test and Fisher’s exact test. Results for continuous and categorical variables are presented as median [Q1–Q3] and number (percentage), respectively. Binary logistic regression analysis was performed to determine the confounder(s) of type D personality in FM. Variables that would be coined as predictors in regression analysis were chosen from statistically significant variables determined by Mann–Whitney U test and Pearson’s chi-squared test.

Sample size estimation was performed by Power Analysis and Sample Size Software, version 11.0 (PASS, NCSS Statistical Software, Kaysville, UT, USA). Accordingly, the sample size was determined as 65 FM patients to calculate the prevalence of type D personality as 30% with a deviation of 25% in the range of 22–38% with 80% power.

Results

A total of 130 participants, consisting of 70 FM patients and 60 controls, were included in the study. The socio-demographic variables of the study population are summarized in Table 1. Median (IQR) disease duration was 5.0 (2.0 − 9.3) years in FM patients. Type D personality was observed in 58.6% and 21.7% of the patient and control groups, respectively (p < 0.001).

Table 1 Socio-demographic variables of study population
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According to categorical evaluation of self-esteem and psychosomatic symptoms, 1.4%, 18.6%, and 80.0% of the patients had low, moderate, and high self-esteem, respectively. In the control group, none of the participants had low levels of self-esteem with 11.7% and 88.3% having moderate and high self-esteem, respectively. No statistically significant difference was observed between patient and control groups in terms of self-esteem level (p = 0.147). Of the patients with FM, 30.0% and 55.7% were classified as having a medium number of and many psychosomatic symptoms, respectively. On the other hand, only 14.3% of the patients were classified as having few psychosomatic symptoms. In the control group, 65% had few psychosomatic symptoms. The rest had either a medium number of or many psychosomatic symptoms. There was a statistically significant difference between patient and control groups in terms of the number of psychosomatic symptoms (p < 0.001).

The comparison of clinical variables between FM patients with type D and non-type D personality is given in Table 2. Accordingly, FIQ, BDI, and BAI scores were higher in patients with type D personality than in patients with non-type D personality (p = 0.05, p < 0.001 and p < 0.001, respectively). Health status and self-esteem level were lower in patients with type D personality when compared to those with non-type D personality (p < 0.05 for both). In terms of psychosomatic symptoms, there was no statistical difference between patients with and without type D personality (Table 2).

Table 2 The comparison of clinical variables between FM patients with type D and non-type D personality
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Of the patients, 58 (82.9%) had negative affectivity. Patients with negative affectivity also had higher psychosomatic symptom scores (D7), and BDI and BAI scores than those without negative affectivity (p = 0.023, p < 0.001, p = 0.001, respectively). Forty-three patients (61.4%) had social inhibition. FIQ scores, self-esteem scale (D1), BDI, and BAI scores were higher in socially inhibited patients than in those without social inhibition (p = 0.008, p = 0.024, p < 0.001, p = 0.001, respectively) (Table 3).

Table 3 The comparison of clinical variables in accordance with subscales of type D personality in patients (n = 70)
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When using binary regression analysis to find the relationship between study population and type D personality, the odds of FM were 5.1 times higher (OR = 5.111, 95% CI 2.351–11.115) for patients with type D personality. After adjusting for age and education level, the presence of type D personality was still related 3.6 times more likely to FM (OR = 3.653, 95% CI 1.547–8.625). In addition, binary regression analysis was carried out to determine the predictors of type D personality among patients with FM. After adjusting for anxiety, psychosomatic symptoms, self-esteem, and employment duration, the regression analysis revealed that type D personality could be predicted by the presence of depression (OR = 1.206, Cl 95% 1.076 − 1.353) and lower education level (OR = 0.794, Cl 95% 0.656 − 0.962) (Table 4).

Table 4 Binary logistic regression for unadjusted (crude) odds ratio (OR) and adjusted (corrected) odds ratio (OR), for factors associated with type D personality in patients with fibromyalgia
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Discussion

The current study showed that type D personality was more common in patients with FM than in a healthy control population. Type D personality was closely related to FM. Moreover, Type D personality was found to be associated with anxiety, depression, poorer health status, and lower levels of self-esteem. Psychosomatic symptoms were more frequent among patients with negative affectivity and socially inhibited patients reported poorer health status.

In the present study, type D personality was observed in 58.6% of FM patients, which was twice as higher as in the healthy controls. In the general population, the frequency of type D personality varies from 13 to 34% [7, 32]. According to a population-based study conducted in Japan, the frequency of type D personality in the elderly was 46% [33]. The prevalence can range from 20 to 37% in patients with distinct comorbidities, such as cardiovascular disease [34]. A few studies to date have investigated the frequency of type D personality in FM [5, 6, 34]. Van Middendorp et al. conducted a study evaluating the prevalence of type D personality and its impact on health status in FM. In that study, the authors showed that 56.5% of the patients had type D personality that caused poorer mental and physical health [34]. A study investigating different personality profiles in patients with FM and chronic fatigue syndrome showed that 30% of FM patients had type D personality [6].

The current study showed that type D personality is closely associated with FM alongside several socio-demographic and clinical variables. Lower educational level and shorter employment duration were closely related to type D personality in FM. A study investigating type D personality and its relation with quality of life in patients with psoriasis demonstrated that patients with type D personality had lower education level [35]. Another study carried out in the Netherlands showed that type D personality was associated with lower socio-economic status, including lower education and income [36]. Yoon et al. found that type D personality was more common among unemployed participants [37]. A number of studies have evaluated occupational activity and stress in type D subjects. These studies highlighted that people with type D personality spent more time in occupational activities and perceived their work place as stressful [38,39,40]. Moreover, a recent study evaluating personality and psychopathology by the Minnesota Multiphasic Personality Inventory (MMPI-2) divided FM patients into two clusters based on the presence of negative emotionality and introversion. The authors observed higher hypochondriasis, depression, hysteria, and schizophrenia in both clusters. However, cluster 2, which included subjects with higher negative emotionality and introversion, was in line with type D personality. Finally, they did not find any differences between clusters in terms of marital status, educational level, and occupational status [41].

In the present study, we observed that patients with type D personality had more anxiety and depression than those with non-type D personality. The most plausible explanation for this is the relationship between resilience, which is considered as an important psychological factor that causes changes in pain perception, and type D personality [42]. With respect to the literature, people with type D personality have lower level of resilience, decreased sense of coherence, and worse self-care attitude [43,44,45]. When resilience gets lower, coping with stress and negative circumstances becomes more difficult. In addition, type D personality is a distressed personality, consisting of negative affectivity and social inhibition that have a tight connection with anxiety and depression. Quezweny et al. showed that the prevalence of depression and anxiety was higher in patients with type D personality, 10 years after percutaneous coronary intervention [46].

As another finding of the current study, patients with social inhibition had higher FIQ scores, and thus poorer health status. However, we could not define a direct relationship between type D personality and FIQ. Garip et al. reported higher disease severity in FM patients with type D personality. Furthermore, negative affectivity and social inhibition were also associated with FIQ [5]. In a recent review, the authors discussed the close relationship between physical and social pain in FM. Accordingly, they suggested that some personality traits related to negative emotionality might cause higher emotional distress and maladaptive cognition in either physically or socially painful situations [47]. Moreover, Ablin et al. proposed that personality profile in FM might be divided into two clusters on the basis of several psychological variables. While the first cluster was characterized by lower co-operativeness and self-directedness, lower levels of persistence and reward dependence, higher harm avoidance, higher levels of alexithymia, less social support, lower positivity, and higher frequency of type D personality, the second cluster had the opposite characteristics of the first group. After a series of evaluations, they found that symptom severity was significantly higher in cluster 1 [6].

In the current study, we found lower levels of self-esteem among patients with type D personality when compared to patients with non-type D personality. Lower self-esteem is characterized by decreased self-control and self-confidence, and reduction of cognitive performance. Additionally, lower self-esteem can be related to anxiety and depression, along with higher suicide risk [15, 16, 18, 19]. Previous studies have also found a reduction of self-esteem in FM [20, 48]. Nevertheless, to our knowledge, there are no studies that directly evaluated the association between type D personality and self-esteem in patients with FM. We also determined that the number of psychosomatic symptoms was significantly higher in patients with FM. This result was predictable, given the colossal amount of evidence regarding the increased frequency of psychosomatic complaints in FM [19]. Increased frequency of psychosomatic symptoms in FM also highlights the multifaceted nature of the disease [49].

The present study has some limitations. First, the study included only female patients and the results are not applicable to men with FM. Although a relation between type D personality and FM has been shown, the cross-sectional design has not been able to determine any cause and effect relationship. Last but not least, we did not evaluate the treatment used by FM patients.

In conclusion, type D personality is more frequent in female patients with FM than that in healthy women. Type D personality is closely associated with FM, in addition to being associated with poorer education, lower occupation duration, lower self-esteem, a higher number of psychosomatic symptoms, anxiety, and depression in FM. Socially inhibited FM patients perceive that they have poorer health status. Defining personality traits and psychological tendencies in FM appears to be essential component of patient evaluation. Careful assessment of these factors and their confounders might prove beneficial to the improved management of patients with FM.