The abnormal reward network associated with insomnia severity and depression in chronic insomnia disorder

Previous research has shown that acute sleep deprivation can influence the reward networks. However, it is unclear whether and how the intrinsic reward network is altered in chronic insomnia disorder (CID). In the present study, we aimed to investigate whether the reward network is altered in patients with CID using resting-state functional magnetic resonance imaging (fMRI) data. Forty-two patients with CID and 33 healthy controls (HCs) were enrolled and underwent resting-state fMRI. Nucleus accumbens (NAc) - based functional connectivity (NAFC) was evaluated to explore the differences in the reward network between the CID and HC groups. Pearson correlation analysis was used to evaluate the clinical significance of altered NAFC networks. Compared to those in the HC group, increased NAFC was found in the salience and limbic networks, while decreased NAFC was found in the default mode network (DMN) and within the reward circuit in patients with CID. In addition, decreased FC between the NAc and DMN was associated with insomnia severity, while NAFC within the reward network was associated with depression symptoms in patients with CID. These findings showed that the reward network is dysfunctional and associated with depression symptom in patients with CID. Future studies of CID should consider both insomnia and depression symptoms to disentangle the role of insomnia and depression in the relationship under study.