نشانگان خستگی مزمن و شخصیت: مطالعه کنترل- موردی با استفاده از مدل پنج عاملی جایگزین

Neuroticism is the personality dimension most frequently associated with chronic fatigue syndrome (CFS). Most studies have also shown that CFS patients are less extraverted than non-CFS patients, but results have been inconsistent, possibly because the facets of the extraversion dimension have not been separately analyzed. This study has the following aims: to assess the personality profile of adults with CFS using the Alternative Five-Factor Model (AFFM), which considers Activity and Sociability as two separate factors of Extraversion, and to test the discriminant validity of a measure of the AFFM, the Zuckerman–Kuhlman Personality Questionnaire, in differentiating CFS subjects from normal-range matched controls. The CFS sample consisted of 132 consecutive patients referred for persistent fatigue or pain to the Department of Medicine of a university hospital. These were compared with 132 matched normal population controls. Significantly lower levels of Activity and significantly higher levels of Neuroticism-Anxiety best discriminated CFS patients from controls. The results are consistent with existing data on the relationship between Neuroticism and CFS, and clarify the relationship between Extraversion and CFS by providing new data on the relationship of Activity to CFS.

Chronic fatigue syndrome (CFS) is a poorly understood medical condition characterized by the presence of chronic and persistently debilitating fatigue for at least 6 months. Additionally, the diagnosis requires at least four of the following symptoms: new headaches, muscle and multi-joint pain, tender lymph nodes, recurrent sore throat, sleep disturbances and impaired memory or concentration. These symptoms lead to a substantial reduction in occupational, personal, social and educational status (Fukuda et al., 1994). Estimates of the prevalence of CFS range from 0.2% to 2.6% (Jason et al., 1999, Reyes et al., 2003 and Reeves et al., 2005). Several etiological factors have been proposed, but no consistent explanation of this disorder has emerged. The etiology of CFS is probably multi-factorial (Harvey and Wessely, 2009). It is useful to distinguish among predisposing, precipitating, and perpetuating factors (Prins et al., 2006). Some researchers have suggested that personality plays a predisposing and/or perpetuating role in CFS (Henderson and Tannock, 2004). Unfortunately, studies focused on personality and CFS have generally employed heterogeneous methodologies (i.e., diversity of designs, lack of consensus about case definition, and comparison samples including psychiatric populations), and this heterogeneity constitutes an important limitation in terms of replication and generalization. Most importantly, research in this field has frequently ignored the relevance of normal personality traits. Ignoring the study of normal personality structure could lead to bias in characterizing CFS patients by emphasizing abnormal instead of normal personality traits (van Geelen et al., 2007). Research assessing normal personality in patients with CFS has mostly been carried out within the framework of the Eysenck or the Five-Factor Model (FFM) perspective, using either the Eysenck Personality Questionnaire (EPQ; Eysenck and Eysenck, 1975) or the revised NEO Personality Inventory (NEO PI-R; Costa and McCrae, 1992). Empirical evidence has shown Neuroticism, the disposition to experience negative affect (i.e., anxiety and depression), to be one of the most consistent personality dimensions associated with CFS (Taillefer et al., 2003 and Besharat et al., 2011). However, results regarding Extraversion, the second most widely studied personality dimension in CFS, are less clear. Most studies have shown that CFS subjects are less extraverted than non-CFS subjects (Buckley et al., 1999, Chubb et al., 1999, Deary and Chalder, 2010 and Besharat et al., 2011), but results have not been as consistent as with the neuroticism dimension. For example, in a recent twin study, Poeschla et al. (2013) found that lower extraversion was associated with CFS, and that this relationship might be causal and bidirectional, whereas in the study by Kato et al. (2006), also using twin pairs, extraversion was not significantly associated with CFS. These inconsistencies may indicate the need to assess extraversion more precisely by paying more attention to the different facets of this dimension. A study by Deary and Chalder (2010) found that Neuroticism and Extraversion, assessed with the NEO PI-R, significantly differentiated CFS from control groups. CFS patients scored higher on Neuroticism, and only two out of the six facets of Extraversion, Activity and Gregariousness, were significantly lower in CFS subjects. Findings regarding the other personality dimensions assessed by the EPQ or by the NEO PI-R were less consistent. In this research, we assessed personality with the Alternative Five-Factor Model (AFFM), which has some advantages over the aforementioned models. The AFFM (Zuckerman et al., 1991 and Zuckerman et al., 1993) emerged from a series of factor analyses of scales that had already been widely used in studies of temperament. The traits of the AFFM are measured with the Zuckerman–Kuhlman Personality Questionnaire (ZKPQ; Zuckerman et al., 1993). In this model, Activity and Sociability constitute two separate traits of Extraversion. This differentiation may provide a better understanding of the discriminant role of Extraversion in this illness. In addition, the dimension of Neuroticism does not include either impulsivity or hostility traits, as does the NEO PI-R; instead, specific scales for these two traits are included in the ZKPQ. The objective of this study is twofold: to assess the personality profile of adults with CFS from the AFFM perspective, and to test the discriminant validity of the ZKPQ in differentiating CFS subjects from normal-range controls. The accuracy of the resulting model was tested by a cross-validation procedure described below. It was hypothesized that participants with CFS, compared with a community control sample, would score higher on Neuroticism-Anxiety and lower on Activity and Sociability.