تمایز ظرفیتی غیر طبیعی در آلکسیتیمیا

As an at-risk personality trait, alexithymia includes difficulties attending to, distinguishing among, and verbalizing emotions. While these deficits are typically described as extending to both positive and negative emotions, some research suggests a valence-specific pattern such that alexithymic individuals are under-responsive to appetitive stimuli in particular. As this pattern suggests anhedonia, it is important to assess the degree to which alexithymia and anhedonia are confounded as contributors to appetitive hyporeactivity. A nonclinical sample of 96 adults rated word and picture stimuli on dimensions of valence and arousal. Participants were assessed for alexithymia, anhedonia, and mood disturbance with the Toronto Alexithymia Scale, the Chapman Revised Social and Physical Anhedonia Scales, and the Profile of Mood States, respectively. The subset of alexithymic individuals (n = 12) under-rated the valence of appetitive but not aversive stimuli relative to non-alexithymic peers (n = 13). Arousal ratings for all stimulus types were comparable across groups. Hierarchical regression in the full sample indicated that social anhedonia, which was confounded with alexithymia, contributed negligible variance to appetitive valence ratings. This study adds useful detail to the concept of diminished hedonic capacity in alexithymia by localizing the deficiency to poor affective differentiation rather than to hypoarousal.

Considering that alexithymia is characterized, in part, by difficulty identifying and describing emotions, it may be surprising that alexithymia is associated with depression in clinical and nonclinical samples (Lee and Guajardo, 2011 and Ogrodniczuk et al., 2012). Indeed, depression emerges as the most powerful individual predictor of alexithymia in the general population, prompting cautionary advice that depression be recognized as a potential confound in alexithymia research (Honkalampi, Hintikka, Tanskanen, Lehtonen, & Viinamäki, 2000). Despite the close relation, factor analysis positions them as distinct constructs (Hintikka, Honkalampi, Lehtonen, & Viinamäki, 2001). To explain the elevated rate of depression, it is possible that alexithymic, like depressed (Epp, Dobson, Dozois, & Frewen, 2012), individuals are vigilant for and/or overly reactive to aversive cues in the environment. However, research using emotional Stroop paradigms shows that alexithymic individuals have similar levels of attentional interference to general aversive stimuli compared to their non-alexithymic peers (Lundh and Simonsson-Sarnecki, 2002, Mueller et al., 2006, Pandey, 1995 and Parker et al., 1993), suggesting a normative degree of threat processing. Another possibility is that negative affect in alexithymia is secondary to deficient hedonic capacity (Dubey and Pandey, 2013 and Prince and Berenbaum, 1993) such that depression results from a failure to attend to positive stimuli and/or process positive life events. Inattention to appetitive stimuli has previously been demonstrated in depressed individuals. For instance, relative to healthy peers, depressed subjects recall fewer pleasant words despite comparable recall of unpleasant words (Sloan, Strauss, & Wisner, 2001) and are less responsive to rewards (e.g., Pizzagalli, Iosifescu, Hallett, Ratner, & Fava, 2008). Such lack of reactivity to appetitive stimuli in depression is a more specific characteristic called anhedonia, and the suggestion of reduced appetitive responsivity in alexithymic individuals calls into question the construct boundaries between alexithymia and anhedonia. The little research to address discriminant validity among alexithymia and anhedonia measures presents mixed results. Loas, Fremaux, and Boyer (1997), for example, found no correlation in a nonclinical sample between a physical anhedonia scale and two facets of the Toronto Alexithymia Scale (TAS-20; Bagby, Parker, & Taylor, 1994), even after controlling for physical displeasure and depression. However, Deborde et al. (2006) found that TAS-20 scores were positively correlated with physical anhedonia scores and that the Bermond-Vorst Alexithymia Questionnaire was positively correlated with both physical and social anhedonia among healthy controls. Consistent with this, Prince and Berenbaum (1993) found aspects of alexithymia to be associated with social anhedonia, even after controlling for depression and negative affect. It is unclear, however, to what extent anhedonia is confounded with alexithymia in predicting behavioral hyporeactivity to appetitive stimuli. The purpose of this study was to examine how subjective ratings of valence and arousal for appetitive, neutral, and aversive stimuli vary as a function of alexithymia, while controlling for anhedonia and mood disturbance. Given that few studies have provided evidence of reduced hedonic capacity in alexithymia, it is important to confirm the effect of selective hyporeactivity to appetitive cues and to determine if such an effect generalizes across verbal (word) and nonverbal (picture) stimulus types. A nonclinical sample of young adults was chosen to minimize the effects of confounding variables beyond those of interest. It was hypothesized that (1) high-alexithymic individuals would rate the valence and arousal of appetitive, but not aversive or neutral, verbal and nonverbal stimuli more weakly than would their non-alexithymic counterparts; (2) given that alexithymia and anhedonia are related yet distinct constructs in the general population, it was expected that an inverse relationship between alexithymia and reactivity to appetitive cues would be independent of contributions by anhedonia and/or mood disturbance.

Table 2 provides descriptive statistics for all variables. Means and standard deviations for the TAS-20, Social Anhedonia, and Physical Anhedonia Scales were consistent with those from other young adult samples (Chmielewski et al., 1995, Coffey et al., 2003 and Kwapil et al., 2008). The TAS-20 and Physical Anhedonia scores were normally-distributed. The Social Anhedonia score was positively skewed but successfully normalized with logarithmic transformation.