Neural response to rewards in youths with insomnia

Insomnia and depression are common comorbid conditions in youths. Emerging evidence suggests that disrupted reward processing may be implicated in the association between insomnia and the increased risk for depression. Reduced reward positivity (RewP) as measured by event-related potential (ERP) has been linked to depression, but has not been tested in youths with insomnia.

Twenty-eight participants with insomnia disorder and without any comorbid psychiatric disorders and 29 healthy sleepers aged between 15-24 completed a monetary reward task, the Cued Door task, while electroencephalographic activity was recorded. RewP (reward minus non-reward difference waves) was calculated as the mean amplitudes within 200-300 ms time window at FCz. Two analyses of covariance (ANCOVAs) were conducted with age as a covariate on RewP amplitude and latency, respectively.

Participants with insomnia had a significantly lower RewP amplitude regardless of cue types (Gain, Control, and Loss) than healthy sleepers, F(1, 51) = 4.95, p = 0.031, indicating blunted reward processing. On the behavioral level, healthy sleepers were more prudential (slower reaction time) in decision making towards Loss/Gain cues than their insomnia counterparts. Trial-by-trial behavioral adjustment analyses showed that, compared with healthy sleepers, participants with insomnia were less likely to dynamically change their choices in response to Loss cues.

Dysfunctional reward processing, coupled with inflexibility of behavioral adjustment in decision-making, is associated with insomnia disorder among youth, independent of mood disorders. Future studies with long-term follow-up are needed to further delineate the developmental trajectory of insomnia-related reward dysfunctions in youth.