Reward-seeking behavior in human narcolepsy

Abstract

Study objectives: The hypocretin system enhances signaling in the mesolimbic pathways regulating reward processing and addiction. Because individuals with narcolepsy with cataplexy have low hypocretin levels, we hypothesized that they may be less prone to risk- and reward-seeking behaviors, including substance abuse.

Design: Endpoints were performance on an array of psychometric tests (including the Eysenck Impulsiveness Scale, the Zuckerman Sensation Seeking Scale, the Gormally Binge Eating Scale, and the Beck Depression and Anxiety Inventory) and on the Balloon Analogue Risk Task (BART).

Setting: Tertiary narcolepsy referral centers in Leiden (The Netherlands) and Boston (USA).

Patients: Subjects with narcolepsy with cataplexy (n = 30), narcolepsy without cataplexy (n = 15), and controls (n = 32) matched for age, sex, and smoking behavior.

Interventions: None.

Measurements and results: There was no difference in risk-taking behavior between narcolepsy with or without cataplexy and the control group, as measured using the BART and the array of questionnaires. However, subjects in the narcolepsy with cataplexy group had significantly higher scores on the Eysenck Impulsiveness Scale (p < 0.05), with 10.0% categorized as impulsive, compared to 6.7% of the narcolepsy without cataplexy group and none of the controls. Narcoleptics with cataplexy also scored significantly higher than controls on the Binge Eating Scale (p < 0.05), with moderate or severe binge eating in 23%. On the depression and anxiety scales, all narcolepsy patients, especially those with cataplexy, scored significantly higher than controls.

Conclusions: We found that narcoleptics with or without cataplexy generally have normal risk-taking behavior, but narcoleptics with cataplexy were more impulsive and more prone to binge eating than patients without cataplexy and controls. Our findings shed new light on the relation between sleepiness and impulsiveness. Furthermore, rates of depression and anxiety were higher in all narcoleptic subjects. However, using the current methods, no evidence could be found to support the hypothesis that hypocretin deficiency would affect reward-processing in humans.

Keywords: Narcolepsy; addiction; cataplexy; hypocretin; orexin; reward-seeking; risk-taking; sleep; sleepiness; substance abuse.

Figure 1

Categorical analysis of the results on the Beck Depression Inventory II (BDI-II), the Beck Anxiety Inventory (BAI), the Gormally Binge Eating Scale (BES), and the Eysenck Impulsiveness Scale (EIS) for the groups Narcolepsy with Cataplexy (N+C), Narcolepsy without Cataplexy (N-C), and Controls (Ctrl). Validated cut-off points were used.,,,