Anorexia nervosa (AN) is an eating disorder characterized by a low food intake and often exceeding exercise, leading to a particularly low body × weight proportion. Patients with AN usually report less hunger than healthy controls. Endogenous endocannabinoids (eCBs), specifically the anandamide, have been associated to hunger, as a meal initiator, but research regarding AN and eCB and inconclusive. In this pilot study, we investigated plasma levels of eCB in inpatients with AN during fasting and after eating, both during the acute AN phase and after weight recovery. After an 8-hr fasting period, blood sample was collected from all participants. After that, participants were given a muffin test meal. Blood samples for the investigation of endogenous eCBs anandamide (N-arachidonoylethanolamide [AEA]) and 2-arachidonoylglycerol (2-AG) were then collected after 120 and 240 min. Participants were only allowed to eat and drink what was offered them during the research. AN reported less hunger than controls during fasting and at the end of the experiment. Also, plasma levels of AEA were significantly smaller in AN in comparison with controls in all time points. No significant difference was found for 2-AG plasma levels. After recovery, no significant difference was found for eCB levels. These findings could be interpreted as an AEA deregulation in AN before and after food intake, which persists after weight recovery. These findings may have implications to the pharmacological treatment of AN and to relapse occurring in the disorder.

This chapter was previously published as an original research article on Appetite (Piccolo et al., 2019).

Pain impairs reward processing, and people suffering from physical pain are at high risk of having a persistently low mood. Although individuals with chronic pain have reported reduced reward responsiveness and impaired mood, it is not clear if reward responsiveness and mood are impaired in samples with sub-clinical pain scores otherwise healthy. Investigating a sub-clinical group is essential to disentangle the influence of medication on the behavioural effect of reward on mood and performance. Here, we aimed to examine the effects of reward on mood and performance in a sample of university students divided into a control group without clinically significant pain symptoms (N = 40) and the sub-clinical group with significant pain symptoms (N = 39). We used the Fribourg reward task and the pain sub-scale of the Symptom Checklist (SCL-27-plus) to assess the physical symptoms of pain. A significant positive correlation was found between average mood ratings and average monetary reward in the control group (r38 = 0.42, p = 0.008) and not significant in the sub-clinical group (r37 = 0.12, p = 0.46). The results might yield first insights into the relationship between pain and reward in sub-clinical populations without the confound of medication.

Impaired decision-making under conditions of uncertainty seems to contribute to the expression and maintenance of anorexia nervosa (AN), but it is not clear whether this impairment is a disease state that would remit with treatment, or a persisting trait in patients with AN. To examine this question, a longitudinal study was conducted in 12 female inpatients with AN (age M = 22.2, SE = 1.36), before (Time-1) and after reaching a body mass index of >17.5 kg/m2 (Time-2). Intolerance of uncertainty (IU) was assessed via a decision-making task, the wheel of fortune (WOF). Weight gain at Time-2 was accompanied with significant changes in uncertainty-related performance compared to Time-1 [(Time × Uncertainty), p < 0.05]. At Time-1, reaction times (RTs) varied in function of uncertainty, while at Time-2, uncertainty did not modulate RTs. These findings support a change in decision-making under uncertainty with successful weight-rehabilitation in AN. While IU was present in underweight patients, it became non-significant after weight restoration.