A preliminary study of sleep in adolescents with bipolar disorder, ADHD, and non-patient controls.

Sleep and circadian abnormalities represent core features of bipolar disorder (BD) in adulthood (1). Among adults with BD, compared to healthy controls, investigations document insomnia and reduced need for sleep during mania, both insomnia and hypersomnia during depression, and greater insomnia and more variable sleep and activity patterns during interepisode periods (2). Two studies have provided evidence that BD is associated with delayed circadian phase (3, 4). Moreover, theories of BD have emphasized the possible role of sleep and circadian rhythm instability in the onset and maintenance of mood episodes (2, 5, 6). Despite increasing interest in early-onset BD, few studies have investigated sleep and circadian functioning in this population. Nonetheless, the literature indicates that sleep problems are significant (7). Questionnaire- and interview-based studies report sleep problems among 96–97% of youth with BD (8). Using one night of polysomnography (PSG), Mehl et al. (9) found that children with symptoms of BD (but not official diagnoses) exhibited impaired sleep efficiency, increased sleep-onset latency, and increased awakenings and nightmares compared to healthy peers. The only published study using actigraphy features case reports of two youths with BD who completed 5 to 7 days of actigraphic monitoring (10). Both individuals exhibited symptoms of insomnia, as well as marked diurnal and nocturnal hyperactivity. The use of actigraphy was a strength, but the case study design limits the generalizability of the findings. Sleep functioning in early-onset BD is an essential area of investigation. Sleep is critically involved in mood regulation (11), particularly for individuals with BD, as they may be especially vulnerable to the destabilizing effects of sleep loss (2). Moreover, particular sleep and circadian profiles may serve as endophenotypic markers for BD (12). A current diagnostic challenge involves distinguishing between BD and attention-deficit hyperactivity disorder (ADHD), a much more common childhood-onset disorder (13, 14). However, one large longitudinal study found that the symptom of decreased need for sleep effectively discriminated between youth with BD (39.8%), ADHD (6.2%) and healthy participants (1.1%) (15). Whereas sleep abnormalities have been alleged in youth with ADHD (16), a recent meta-analysis revealed few significant differences between samples with ADHD and healthy groups (17). The current study aimed to extend previous research by examining both self-report and objective estimates of sleep over a four-night period using carefully characterized samples of youth with BD who were between mood episodes, youth with ADHD–combined type (ADHD-C), and healthy adolescents. We chose ADHD-C as our clinical comparator because it is the most common form of ADHD (18), with symptoms of both inattention and impulsivity/hyperactivity, and therefore perhaps most representative of this condition. Based on previous research (19–21), we predicted that participants with BD would exhibit greater total sleep time, but also greater wakefulness during the night, lower sleep efficiency, and lower satisfaction with sleep than their peers. We also hypothesized that the participants with BD would exhibit later sleep onset and morning wake times than their peers (3, 4). These variables were conceptualized as proxies for a tendency toward a delayed phase. Finally, we predicted that the participants with BD would show more variable sleep onset times, morning wake times, and total sleep times than their peers in the comparison groups (20, 22).