تصمیم گیری و تکانشگری در بیماران مبتلا به اختلال تغذیه ای

Impairment in decision-making can be related to some pathological behaviors in eating disorders. This ability was assessed in 71 eating disorder patients (27 restricting type patients and 44 binge/purging type patients) and compared with 38 healthy controls using the Iowa Gambling Task. This task simulates real-life decision-making by assessing the ability to sacrifice immediate rewards in favor of long term gains. Furthermore, some studies have demonstrated a relationship between impulsivity and decision-making, so in our study the Barratt Impulsiveness Scale was also used. Eating disorder patients, both the restricting and the binge/purging groups, performed poorly in the Iowa Gambling Task compared to controls, confirming a deficit in decision-making in these patients. The restricting group showed poorer IGT performance than the binge/purging group. Interestingly, impulsivity was negatively correlated with decision-making, but only in the binge/purging group. In conclusion, our results confirm a specific deficit in eating disorder patients which may be related to their pathological eating behavior, and suggest that this impairment might be explained by different mechanisms in restricting and binge/purging disorders.

Decision-making is defined as the capacity to make decisions about a course of action (Guillaume et al., 2010). Impairment in this cognitive function can be related to some pathological behaviors. The Iowa Gambling Task (IGT) (Bechara et al., 1994) is an experimental test which simulates real-life decision-making in situations that involve uncertainty, reward and punishment. Performance on this task has been shown to be sensitive to ventromedial prefrontal cortex (VMPFC) and limbic system functioning, so that patients with damage to VMPFC showed impaired performance on the IGT compared to control subjects (Bechara et al., 1999). Like patients with VMPFC lesions, some mental disorders have also shown impairment in the IGT, such as substance abuse and dependence (Grant et al., 2000, Bechara and Damasio, 2002, Dom et al., 2006 and Verdejo-García et al., 2007), obsessive-compulsive disorder (Cavallaro et al., 2003 and Lawrence et al., 2007), pathological gambling (Goudriaan et al., 2006 and Linnet et al., 2006) and eating disorders (Cavedini et al., 2004, Cavedini et al., 2006, Tchanturia et al., 2007, Liao et al., 2009 and Tchanturia et al., 2012). Patients with these disorders show an inability to make advantageous decisions and a preference for immediate reward in spite of future negative consequences. With regard to eating disorders, some studies have found decision-making impairment in anorexia nervosa (AN) restricting and binge/purging types (Cavedini et al., 2004, Cavedini et al., 2006, Tchanturia et al., 2007 and Tchanturia et al., 2012), in AN restricting type (Abbate-Daga et al., 2011), in bulimia nervosa (BN) (Boeka and Lokken, 2006) and in both AN and BN (Liao et al., 2009 and Brogan et al., 2010). To our knowledge, only Guillaume et al. (2010) and Bosanac et al. (2007) failed to confirm this deficit in samples of AN and BN patients, compared to controls. In Guillaume et al. (2010) patients were euthymic and free of medication, whereas in Bosanac et al. (2007) a very modest sample size was used, which may explain inconsistent results with other studies. Regarding differences in the IGT net score between patients and healthy controls, Tchanturia et al. (2012) reported medium to large effect sizes between AN patients and controls (Cohen's d=0.64 for males; Cohen's d=0.72 for females). From data reported in other studies, we found large effect sizes between AN and controls in Cavedini et al. (2006) (Cohen's d=0.98) and in Abbate-Daga et al. (2011) (Cohen's d=1.0). The effect sizes of the rest of the studies could not be calculated due to the absence of required data. Moreover, Cavedini et al., 2004 and Cavedini et al., 2006 compared IGT performance between AN restricting type (AN-R) and AN binge-eating/purging type (AN-BP), reporting differences between them, with a significantly greater impairment in AN-R type. On the contrary, no other studies compare these groups, so no definite conclusions can be drawn with respect to restricting and binge/purging types. Another limitation of some of these studies is that a larger sample size would have been desirable. Thus, there is evidence that eating disorder patients have a decision-making deficit, but more data are needed to confirm possible differences in decision-making ability among eating disorder types. Besides, there is recent research on personality traits underlying decision-making deficits. Of the different personality characteristics, impulsivity has been the most studied, as it involves acting without planning and without considering the consequences of that behavior, which might be associated with long-term losses. In fact, some studies showed a negative correlation between impulsivity and IGT performance in the general population (Zermatten et al., 2005 and Davis et al., 2007). However, in eating disorder patients, Liao et al. (2009) found no correlation between impulsivity and IGT performance. Nor did they find this correlation in a sample of women with AN or in women with BN. Similarly, Tchanturia et al. (2012) did not find this association in a sample of men with AN. In these studies the authors do not specify the results separately in different eating disorder groups. It is known that AN and BN patients differ clearly in impulsivity, with higher levels in the latter (Cassin and von Ranson, 2005). Within AN patients, there are also significant differences in personality characteristics, with the AN-R type being related to perfectionism and rigidity, while impulsivity is more associated with the AN-BP type (Fassino et al., 2004). Thus, regarding personality traits, the AN-BP group is closer to the BN group than to the AN-R group (Fassino et al., 2004). In short, there is some evidence that AN-R type shows poorer IGT performance than AN-BP type (Cavedini et al., 2004), and that both AN subtypes and BN show poorer IGT performance than healthy controls. As decision-making has been related to impulsivity in some studies, and as AN-BP subtype and BN patients show higher levels of impulsivity than AN-R patients, the present study was designed to examine decision-making using the IGT in AN-R patients (restricting group) on the one hand, and in AN-BP and BN patients (binge/purging group) on the other. The second aim of this study was to explore whether there is a link between impulsivity and decision-making in both groups separately. The control group was needed just to compare the IGT performance of eating disorder patients with that of healthy controls. It is for this reason that the impulsivity measure was not administered to the control group. Considering the previous findings, we tested the following hypotheses: (a) eating disorder patients, both the restricting and the binge/purging group, will show a decision-making impairment in comparison to healthy controls; (b) the restricting group will show poorer IGT performance than the binge/purging group; and (c) impulsivity will be associated with poorer performance in the IGT in both groups. However, the second and third hypotheses have to be taken as preliminary, as previous studies are scarce and give inconsistent results.