The present study was designed to characterize sleep quality and to examine the association between mood and sleep in BD I youth with recent manic episodes. In the acute manic phase, children with bipolar I disorder experience a decreased need for sleep, clinically seen with difficulty falling asleep and frequent nighttime awakenings. The goal of treatment is often to make these children sleep and often an increase in sleep time is seen due to medications and/or recovery from manic episode. Sleep may therefore be a response marker and a therapeutic target in mania. The results of this study indicate that, compared to demographically similar healthy controls, adolescents with bipolar I disorder are indeed characterized by distinct patterns of sleep disruption. Consistent with our hypothesis, BD teens had longer sleep onset latency, a greater number of nighttime awakenings, and greater total time awake during these awakenings than did typically developing HC teens. BD and HC participants slept more during weekend nights than during weeknights, but mood symptoms contributed to sleep disturbances within the BD group. For example, total time awake was associated with decreased need for sleep, increase in goal directed activity, and an increase in productivity in the BD group. The total number of nighttime awakenings was associated with elevated/expansive mood, an increase in productivity, and worsening evening mood, which was also associated with longer sleep onset latency. Our hypothesized discrepancy between parent and teen report of sleep quality was found with the number of nighttime awakenings reported.
Our findings are consistent with those of previous studies indicating a decreased need for sleep as a common presenting symptom for pediatric BD [14
]. Consistent with previous studies of bipolar spectrum children [21
], we found a significant difference between BD and control groups for increased sleep onset latency. We also found, however, decreased need for sleep and longer sleep onset latency to be associated with quantified sleep variables. Our finding of significantly greater number of times awake for the BD group compared to controls is consistent with actigraphic data of decreased sleep continuity and efficiency [26
]. Similar to [24
], we found that depressed mood was positively associated with increased sleep length time. Mood symptoms associated with PSQI based sleep variables included worsening evening mood, excessive/inappropriate guilt, feeling unloved, and self-injurious behavior. While it is logical that a worse mood in the evening would lead to difficulties sleeping, these relations should be explored further, as they may place a child at increased risk for progression of both sleep dysfunction and mood symptomatology.
Many of the BD subjects also were experiencing manic, mixed, or depressive symptoms at the time of assessment, all of which may be associated with sleep disturbances. The finding of greater sleep time on the weekends is consistent with Carskadon’s findings that teens sleep more on the weekends than on weeknights [36
]. We found this to be true even for BD teens, the majority of whom were still in a mood episode. However, it is difficult to conclude whether the increase in weekend sleep time the BD group reported was sufficient enough recovery sleep, as the amount of reported and calculated weekend sleep was comparable to the HC group. Further studies using outcomes specifically measuring sleep recovery with and without mood symptoms are warranted.
Over two-thirds of the BD sample was medicated, which can also affect sleep as treating sleep disturbance in BD is a common clinical practice, and many of the medications used to treat BD cause somnolence. In addition, previous studies suggest that treating sleep disturbances in mania leads to more positive outcomes, including shorter inpatient stays [43
]. Surprisingly, the medicated subsample (N = 21) of the BD group did not sleep significantly more hours than the unmedicated (N = 6) subjects, nor were any significant group differences found in analyzing the sleep variables of the medicated subsample. In addition, only three of our patients were euthymic at time of assessment. Larger sample sizes would be needed to better interpret subgroup analyses of medication, sleep, and mood between medicated and non-medicated BD. Whether the teens required better control of current mood symptomatology to improve sleep or whether they needed more sleep to improve mood requires further investigation.
With BD children at higher risk for suicidality and impulsivity, does impulsivity and negative mood states lead to sleep disturbances? Conversely, does lack of sleep or sleep disturbances increase impulsivity and negatively affect mood? While it is clear that self-injurious behavior is often impulsive [46
], our finding that self-injurious behavior was associated with increased sleep onset latency indicates that this sort of impulsive behavior combined with mixed mood states may lead to sleep disturbances. Previous literature supports the idea that adults in mixed states have increased impulsivity, substance use, and suicide attempts [47
]. In a study of BD youth 7–17 years old, non-suicide attempt SIB was associated with greater lifetime number of mixed episodes [48
]. However, neither of these studies directly relates impulsivity or mood states with specific sleep patterns. Among the few studies examining the relations among impulsivity, mood, and sleep, Schmidt et al. [49
] showed that insomnia (initial, middle, and/or terminal) in undergraduate students was associated with impulsivity characterized by actions completed without thinking when upset. This impulsivity led to greater negative bedtime thoughts and emotions that were then associated with more severe insomnia. Therefore, based on these latter studies and our finding, it may be useful to address negative bedtime thoughts and emotions with behavioral therapies to decrease impulsivity and improve sleep [49
HC parents may have showed more reporting discrepancy than BD parents because the former do not observe their teen’s sleep patterns as vigilantly as do their counterparts, particularly in this group of newly diagnosed BD youth with perhaps higher parental concern if the teens are reporting sleep disturbance. With all subjects, more discrepancies were found between teen and parent reporting for weekends rather than weeknights, suggesting that parents may be more aware of sleep patterns in their teens when their children have to wake up in time to attend school. Significant correlations between reported and calculated sleep for parent-teen BD reporting suggest that bedtimes and awakening times are accurately noted.
Our findings echo the conclusion of Lofthouse et al., who found that parent–child concordance is low when reporting on sleep symptoms in youth with bipolar spectrum disorders [21
]. Tillman et al. also showed low parent–child concordance in a population of bipolar spectrum disordered children ages 7–14 for reports of symptoms of mania, including the symptom of decreased need for sleep (kappa .07) [23
]. Owens et al. found that healthy elementary school aged children reported greater nighttime awakenings than did parents, consistent with our findings for all the subjects in our study [34
]. No studies to our knowledge have examined discrepancies between parent and teen reporting using quantified sleep variables, or examined the associations between mood and these sleep variables. Our study is also the first to focus on adolescents with a recent onset of fully syndromal mania, rather than the spectrum of bipolar disorders with variable onset and course described in previous bipolar sleep studies in youth.
Limitations to this study include the fact that data are based on self-report. However, the WASH-U KSADS semi-structured clinical interview provided another source of supporting evidence of our results. We based our sleep analysis on a previously validated sleep scale (PSQI [42
]) but did not use actigraphic data to provide more objective measures of sleep-related activity. It is important to note, however, that Goldberg et al. demonstrated that self-reported measures of sleep in BD adults have been shown to have internal consistency, construct validity, discriminant validity, and test–retest reliability [51
]. Subgroup comparisons were limited by sample size, such that the effect size of analyses of mood state, sleep, and medications used in medicated versus unmedicated patients, of which there were few, was too small to provide a clinically significant interpretation. However, the sample of BD subjects ascertained for this study uniformly had BD I with few co-occurring psychiatric illnesses or other sources of heterogeneity. Other areas of sleep dysfunction that may potentiate mood symptoms and vice versa were not explored. For example, parasomnias such as confusional arousals are associated with a 13 times higher occurrence in adults with BD in a general population sample [52
]. It would be important to include a study of other characteristics of sleep dysfunction as this may also affect nighttime awakenings and total time awake. Finally, this study represents sleep symptoms exhibited only at around the time of assessment and based on retrospective report of past mood symptoms. Future studies should examine such symptoms longitudinally to determine their course and influence on outcome.
Despite these limitations, this study characterized distinct sleep disturbances in adolescents with bipolar I disorder including longer sleep onset latency, greater number of nighttime awakenings, and greater total time awake during these awakenings compared to typically developing youth. Prospective assessments of sleep in teens with recent manic episodes will aid in clarifying how sleep quality changes with different mood states and whether sleep quality in euthymic BD subjects is more similar to that in HC participants. Creating a separate validated consensus rating of parent and child report as is done in other assessments such as the WASH-U KSADS, YMRS, and CDRS-R may also provide an accurate measure of sleep in this population. Future studies including objective actigraphic and polysomnographic data would be useful to associate with the subjective findings of sleep disturbance and mood found in this study. These objective studies would also clarify the effect of medications on sleep and mood. While historically difficult to study manic patients in monitored sleep studies, it would be useful to conduct such studies while the child was experiencing a depressed or mixed state, given that many in our BD group were in such states. Studies of both macroarchitecture to describe sleep onset latency, REM, and specific sleep stages, and microarchitecture using quantitative EEG [53
] would aid in further clarifying and understanding the biological mechanisms [54
] by which bipolar mood states affect sleep, and therefore direct clinical interventions. Beyond advising families of youth with BD to track sleep patterns daily, use goal setting to regulate the sleep-wake cycle, and provide psychoeducation regarding good sleep hygiene, few studies have examined the application of current sleep therapies to youth with BD. Interpersonal and social rhythm therapy (IPSRT) focuses on addressing circadian rhythm disruptions via sleep and social routines. In a recent study of IPSRT in adolescents with BD, Hlastala et al. found significant decreases in manic, depressive, and general psychiatric symptoms and overall increase in global functioning over 20 weeks [55
]. Additionally, cognitive behavioral therapy (CBT) for insomnia, family-focused intervention, CBT for BD, and light therapy all address elements of sleep dysfunction and may be appropriate for regulation of the sleep –wake cycle in BD [53
]. Medications to help motivate and awaken depressed BD patients and to aid with insomnia can also help regulate this cycle [56
]. By discovering when and how sleep architecture is disturbed and how it is associated with mood, the optimum time for intervention with these possible therapies can be determined.