OBJECTIVE: Accumulating evidence has suggested bidirectionality between sleep problems and depression, but the underlying mechanism is unclear. We assessed the role of sleep in inhibitory control ability with emotional stimuli, which has been shown to be suboptimal among individuals with depression and proposed to perpetuate depressive symptoms. METHODS: Emerging adults (aged 18-25 years, 64.6% female) were screened for depressive and other mental disorders by structured clinical interview and questionnaire. Individuals with depressive disorders were assigned to have a polysomnography-monitored daytime sleep opportunity (Sleep-Dep, n = 20), whereas nondepressed individuals were randomized to either have daytime sleep (Sleep-Ctrl, n = 27) or stay awake (Wake-Ctrl, n = 18). Participants completed the Affective Go/No-Go Task two times, separated by experimental conditions. RESULTS: a factorial model with a between-subject factor (Sleep-Dep/Sleep-Ctrl/Wake-Ctrl) and a within-subject factor (test 1/test 2) was used to assess if the groups differed in inhibitory control across test sessions, as inferred by changes in d-prime and false alarm rates (FA). Results from mixed factorial models showed a significant interaction effect between time and group on FA in the block with neutral faces as the target and happy faces as the nontarget (F(2,61) = 5.15, pfdr =. 045). Although Sleep-Dep had decreased FA after sleep (t(19) = 2.94, pfdr =. 050), Sleep-Ctrl and Wake-Ctrl had no significant between-session changes (p values >. 05). Postsleep improvement in FA in Sleep-Dep correlated with longer stage 2 sleep (r(20) = 0.788, pfdr <. 001) and stage 2 fast spindle number at O1 (r(18) = 0.692, pfdr =. 015). CONCLUSIONS: Sleep gain, particularly stage 2 sleep and related physiology, potentially enhances inhibitory control ability responding to emotional information among individuals with depressive disorders.

We assessed the effect of a daytime sleep opportunity on planning and risk-related decision-making in emerging adults using multiple neurobehavioral assessments. A total of 136 healthy emerging adults (20.0 ± 1.5 years), 65% female, performed the Risky-Gains Task and the Tower of London test twice. Between these assessments, they were randomized to either have a sleep opportunity monitored by polysomnography (Sleep group, n = 101) or to stay awake (Wake group, n = 35). During Test 2, in comparison to the Sleep group, the Wake group showed increased sleepiness, worse planning ability and more decrease in reaction times when selecting risky choices. Changes in Tower of London test steps used and Risky-Gains Task response time correlated with the number of central and frontal fast sleep spindles, respectively. These results indicate that among emerging adults who commonly have poor sleep patterns, a daytime sleep opportunity was related to better planning ability, better psychomotor vigilance and stable response speeds in risk-related decision-making. Changes in planning and risk-related decision-making correlated with the number of sleep spindles during the nap, supporting a specific role for sleep in modulating planning and potentially other higher-order cognitive functions.

Adolescents and young adults continue to develop rapidly, especially in their high cognitive functions such as working memory. Sleep and regular exercise have been shown to affect brain and cognitive functions, and we investigated the interplay between these two factors on working memory. One hundred participants completed a sleep-exercise log, wore an acti-watch for five days and performed a working memory task on the sixth day. Regular exercisers were found to have significantly faster response time on the working memory task than non-regular exercisers, and such effect was moderated by actigraphy-measured total sleep time. In other words, regular exercisers had faster reaction time than non-regular exercisers only when they had sufficient sleep (>6.5hours). Our findings showed that both healthy sleep and regular exercise habits should be promoted among adolescents and young adults to optimize cognitive development.