اولویت صبحگاهی ـ شبانگاهی و اختلالات تغذیه ای

The aim of this work was to attempt to clarify the relationship between eveningness preferences and eating behaviour. In a survey a sample of 270 females (146 recruited in a treatment centre for eating disorders and 124 control) was administered the reduced version of the morningness–eveningness questionnaire (MEQr) and the eating disorder inventory 2 (EDI-2). A significant higher percentage of evening-type in patient versus control group was observed. About 46 patients who participated in the survey were enrolled in a further prospective study. A significant regression of symptomatology as scored by EDI-2 corresponded to a significant increase in MEQr scores (i.e. shift towards morningness). We concluded that altered eating behaviours could modulate circadian preference. The results are discussed in relation to possible applications for clinical treatment.

Most biological and behavioural parameters present a rhythmicity synchronised with the light–dark environmental cycle (24-h period or circadian rhythm). Their endogenous origin has been proven to the extent that they continue to present the same behavioural patterns even when there is no environmental input (Wehr, 1996). However, people living under the same environmental conditions and with similar daily activities present rhythmic variations that differ according to the parameters considered. It has been shown that there are individual differences that affect the expression of circadian rhythms. One of the most robust individual difference is the morningness–eveningness preference or circadian typology (morning-, intermediate-, and evening-type), which seems to be based on endogenous rhythmic control (Kerkhof & Van Dongen, 1996). Systematic investigations in chronobiology and chronopsychology have extensively described the differences between extreme groups in circadian rhythmicity. Morning-types display a phase advance in the peak of body temperature (121 min) and alertness (171 min), and in the sleep–wake cycle (80 min) and performance (from 1 to 6 h depending on the type of task) compared with evening types (Kerkhof, 1985 and Tankova et al., 1994). Circadian typology might reflect an underlying difference in the synchronisation of the biological clock with the environment (Natale & Adan, 1999). The morning-type pattern is more synchronised or entrained with environmental (e.g. light–dark cycle) Zeitgeber (i.e. forcing environmental oscillation which entrains a biological self-sustaining rhythm) than the evening type. Moreover, females often appear to be skewed toward a morningness pattern when they are compared to males (Adan and Natale, 2002 and Randler, 2007). Morningness–eveningness preference is not a fixed feature but can change during the span of an individual’s life. Morning preference is more frequent until 10 years and after 50 years (Roenneberg et al., 2004). Nevertheless, scientists have encountered substantial difficulties in attempting to give an exhaustive explanation of morningness–eveningness preference. Thus, it remains to clarify whether the development of circadian rhythms is determined mainly by biological (Katzenberg et al., 1998), environmental (Natale, Adan, & Chotai, 2002) or cultural factors (Caci et al., 2005 and Shinomiya et al., 2004). A greater tendency towards eveningness has been observed in different behavioural disorders: bipolar disorder (Hakkarainen et al., 2003), depression (Chelminski et al., 1999 and Drennan et al., 1991), drug addiction (Adan, 1994), impulsivity (Caci, Robert, & Boyer, 2004), and seasonal depression (Johansson et al., 2003, Johansson et al., 2004, Murray et al., 2003 and Natale et al., 2005). It is still not clear if eveningness in itself might reflect a premorbid trait or an aspecific risk factor for behavioural diseases (Chelminski et al., 1999) or, rather, if the misalignment amongst biological clock and other rhythms, such as social (social jet-lag – Roenneberg, Wirz-Justice, & Merrow, 2003), plays an important role in modulating psychological well-being (Natale et al., 2005). A possible relationship between eveningness preference and eating disorders has also been suggested (Kasov, 2001 and Tortorella et al., 2007). The tendency to eat in the evening is more prevalent amongst individuals who binge frequently than amongst weight-matched controls (Greeno et al., 1995 and Rand et al., 1997). Both binge and purging are substantially more probable in the evening than during the day, independently from setting, occupation, and day of the week (Johnson et al., 1995 and Mitchell et al., 1991). In other words eveningness should increase the probability of binging and purging, increasing the number of waking hours spent during the evening versus day. Binging and purging, therefore should occur more frequently in people biased more towards eveningness than morningness. This hypothesis is consistent with a study by Latzer, Tzischinsky, Epstein, Kklein, and Lavie (1999), who used ambulatory actigraphic monitoring to assess sleep–wake patterns in bulimic patients and control participants. Although the two groups did not differ in total sleep time or in sleep quality indexes (like sleep latency, sleep efficiency, and motor activity) the bulimic patient’s mean time of sleep onset and awaking were approximately 1 h later than those of control participants. The possible link between circadian typology and eating behaviours could be supported both by biological and personality factors. In the past 10 years, strong evidence has accumulated showing that timing of sleep can be genetically determined (Archer et al., 2003 and Katzenberg et al., 1998). Eating disorders are characterised by a disruption of circadian feeding pattern as well as by alterations in the circadian rhythms of hormone release. Those, a possible role of gene polymorphism in the biological vulnerability to eating disorders may by suggested (Tortorella et al., 2007). In the same way many investigations have shown that extreme circadian typology groups significantly differ in cognitive styles (Fabbri, Antonietti, Giorgetti, Tonetti, & Natale, 2007) and personality traits (Cavallera and Giudici, 2008 and Diaz-Morales, 2007). The individual profile describes a morning type as who processes information using consolidated schema and considering social norms and rules. On the contrary, the evening-type profile describes a person who processes information through emotional parameters, who builds new and original schema, and is highly creative but lacks of self-confidence in social relationships. Eveningness is positively correlated to novelty seeking, whereas it was negatively correlated to conscientiousness. Consequently, evening types have a less healthy lifestyle than morning types (Adan et al., 2006 and Taillard et al., 2001). Even if a specific personality profile relative to eating disorders does not exist (Claes et al., 2006 and Lilenfeld et al., 2006), the above mentioned personality features could support the prevision of a high correlation between eveningness and eating disorders. The aim of the present study was to analyse the relationship between eating disorders and eveningness in a survey (including both patient and control subjects) and in a prospective research (analyzing eating symptomatology and eveningness in patient with eating disorders along the firsts 6 months of the psychotherapeutic treatment).

A possible link between eveningness preference and eating disorders has been suggested (Kasov, 2001 and Tortorella et al., 2007). In the survey study, we did not find any correlation between MEQr and EDI-2 scores. However, we found that the evening-types percentage was twice in clinical sample in comparison to control sample. Moreover MEQr scores were significantly higher (i.e. less eveningness) in the control sample in comparison to the clinical sample. Results from prospective study, showed that along psychological treatment MEQr score tend to increase (shift towards morningness) as well as clinical symptoms regress as assessed by EDI-2. Each of analyses used in the present work has its own limitation, but it was interesting to observe each provided concordant and complementary results. It may be concluded that, eating behaviour seems to modulate circadian preference and not vice versa. Such hypothesis should be further evaluated through studies enrolling a higher number of patients with eating behaviour disorder. It should be also important to distinguish across different eating disorders. If these results were confirmed, they could have important repercussions in the therapeutic field (Grandin, Alloy, & Abramson, 2006): for instance, greater attention could be paid in therapeutic programs to circadian Zeitgebers able to prompt an advancement of the phase of the biological clock; or again, light therapy could be used or sleep–wake cycle manipulation. References