Human sleep is regulated by a two-process model comprised of a homeostatic sleep–wake component (referred to as Process S) and a circadian component (referred to as Process C, see also Chapter 2) (Borbély & Achermann, 1999; Borbély, 1982; Borbély, Achermann, Trachsel, & Tobler, 1989). The homeostatic sleep–wake component specifies that there is an increased need to sleep as the period of wakefulness increases (i.e., sleep pressure), with sleep pressure increasing the longer an individual is awake and reducing as sleep occurs. The homeostatic process interacts with the circadian component of the two-process model which is an “internal clock” system that is responsible for regulating the 24-hour rhythm each day (i.e., circadian pacemaker). The secretion of melatonin, a hormone produced by the pineal gland in humans, is reliably linked to the circadian system (Cajochen, Krauchi, & Wirz-Justice, 2003; Klerman, Gershengorn, Duffy, & Kronauer, 2002). The homeostatic process and circadian pacemaker interact on a continual basis and drives the timing and intensity of sleep (Borbély, Daan, Wirz-Justice, & Deboer, 2016). Ideally, the homeostatic and circadian systems work in sync to optimally regulate sleep, but the various biological, environmental, and contextual changes that occur in adolescence can disrupt this balance and contribute to sleep and/or circadian disturbances.

Significant neurodevelopmental changes, including brain reorganization and synaptic pruning, occur in the transition from childhood to adolescence (Sisk & Foster, 2004), and these changes in turn impact sleep architecture (Colrain & Baker, 2011; Dahl & Lewin, 2002; Spear, 2000). Slow wave sleep (SWS) decreases across adolescence (Colrain & Baker, 2011; Ohayon, Carskadon, Guilleminault, & Vitiello, 2004), with both delta and theta power assessed with sleep electroencephalogram (EEG) beginning to decline around age 11 (Campbell & Feinberg, 2009). These changes in the adolescent EEG, corresponding with a decrease in gray matter brain tissue, are believed to be due to synaptic pruning that occurs as part of adolescent brain maturation (Campbell & Feinberg, 2009; Feinberg & Campbell, 2010; Whitford et al., 2007).

These changes in neurodevelopment may impact or interact with sleep–wake homeostasis (Spear, 2000), as more physically mature adolescents accumulate sleep pressure more slowly than less physically mature adolescents (Jenni, Achermann, & Carskadon, 2005; Taylor, Jenni, Acebo, & Carskadon, 2005). For example, Jenni et al. (2005) found sleep pressure during wakefulness to be slower in mature adolescents (Tanner stage 5) compared to prepubertal/early pubertal adolescents (Tanner stage 1 or 2), leading the authors to conclude that “maturational changes of homeostatic sleep regulation are permissive of the sleep phase delay in the course of adolescence” (p. 1446). That is, maturational changes that impact homeostatic sleep regulation contribute to adolescents likewise experiencing an increase in eveningness preference (a developmental shift from being a “morning lark” to an “evening owl”), which peaks around age 20 years before beginning to decline across adulthood (Roenneberg et al., 2004). These homeostatic and circadian factors often lead to weekend phase delay whereby starting around 9 years of age (Thorleifsdottir, Bjornsson, Benediktsdottir, Gislason, & Kristbjarnarson, 2002), adolescents try to “catch up” on sleep on weekends when the weekday demands requiring an early rise time such as school are less pressing. This is an important consideration in studies examining adolescent sleep, as weekend delay or catchup is itself associated with functional outcomes (O’Brien & Mindell, 2005; Wolfson & Carskadon, 1998), including poorer attentional functioning (Kim et al., 2011). Nevertheless, how these neurodevelopmental and maturational changes relate specifically to adolescents with ADHD is unknown and a clear area for future research (Becker et al., 2015; Kirov & Brand, 2014; Owens et al., 2013). For example, youth with ADHD have lower gray matter volumes than their peers (Castellanos et al., 2002), though this group difference may reduce across development (Nakao, Radua, Rubia, & Mataix-Cols, 2011) and it is unknown how changes in brain functioning in adolescents with ADHD relates to sleep. One recent twin study found that ADHD and poorer sleep quality were associated because of genetic (55%) as well as nonshared environmental (45%) influences; further, it was persistent ADHD that was linked to poorer sleep quality in young adulthood suggesting that it may be underlying brain vulnerabilities that contribute to the associations between ADHD and sleep quality (Gregory, Agnew-Blais, Matthews, Moffitt, & Arseneault, 2017) (see, however, Gau & Chiang, 2009; for conflicting findings). In addition, studies indicate that children (Gruber et al., 2012) and adults (Kooij & Bijlenga, 2013) with ADHD may have a later circadian rhythm and/or preference than their peers, though circadian rhythm/preference remains unexamined in adolescents with ADHD.

In line with the theme of this book, the focus of this chapter is sleep in adolescents with ADHD specifically. This is certainly a topic of theoretical, empirical, and clinical importance. In addition, as the study and treatment of sleep in adolescents with ADHD advances, it may prove useful to draw from other areas of research such as depression and bipolar disorder that currently have a much larger body of research. ADHD is associated with high rates of comorbidity (Pliszka, 2015), and it is likewise clear that there is high comorbidity between sleep and most, if not all, psychiatric disorders (Benca, Obermeyer, Thisted, & Gillin, 1992). There is growing interest in sleep as a potentially transdiagnostic mechanism that contributes to the presence and persistence of mental disorders and their associated impairments (Harvey, 2008; Harvey, Murray, Chandler, & Soehner, 2011). As noted by Harvey et al. (2011), “a transdiagnostic perspective raises the possibility that disorders co-occur because they share common mechanisms (sleep disturbance being one candidate)” and the authors further note that an “advance of the transdiagnostic perspective is that it could lead to more rapid transfer of advances to a broader range of disorders” (p. 226). What might this mean for understanding sleep in adolescents with ADHD? First, sleep disturbance may also be viewed as one mechanism linking ADHD to range of other psychiatric disorders. Second, researchers interested in sleep in the context of adolescent ADHD likely do not need to build from the ground up and instead can draw from broader literatures examining sleep and circadian systems. In turn, substantive advances in the neurobiology (e.g., disturbed serotonergic and dopamine systems), phenomenology (e.g., emotion dysregulation), and treatment of sleep/circadian disturbances in adolescents with ADHD may occur more quickly. An example of this possibility is considered later in describing ways that one existing cognitive–behavioral sleep intervention may be used and potentially adapted for adolescents with ADHD. As will become clear next, surprisingly little rigorous research has examined sleep in adolescents with ADHD, and the transdiagnostic framework offers a useful springboard for advancing this area of empirical and clinical importance.

Most studies examining sleep in relation to adolescent ADHD have relied on subjective measures, with studies generally finding adolescents with ADHD (or elevated ADHD symptoms) to have poorer sleep and more sleep disturbances than adolescents without ADHD (Chiang et al., 2010; Fisher et al., 2014; Gau & Chiang, 2009; Gau et al., 2010; Lufi & Tzischinsky, 2014; Yang, Shang, & Gau, 2011). Still, surprisingly few studies have examined patterns and prevalence of subjectively measured sleep problems in adolescents with ADHD. In a study of 93 adolescents (ages 11–16 years) with a childhood diagnosis of ADHD in Taiwan, 40% met criteria for a sleep disorder diagnosis using a semistructured diagnostic interview, compared to 18% of matched comparison adolescents (Gau et al., 2010). In a multicenter observational study in Italy, 23% of youth with ADHD had a sleep disorder as assessed with a diagnostic interview, compared to 13% of youth without ADHD, though the sample spanned childhood and adolescence (ages 5–17 years; N=2861) and rates in adolescents specifically were not described (Reale et al., 2017). A study in Israel of adolescent males (ages 13–15 years; N=100) attending a special school following failure in other educational environments found a later self-reported bedtime among males with ADHD compared to males without ADHD, with 64% of males with ADHD going to bed after 2:00 a.m. compared to 16% of males without ADHD (Weinstein, Yaacov, Manning, Danon, & Weizman, 2015). In a sample of 262 young adolescents (ages 10–15 years) diagnosed with ADHD in the United States, almost three-quarters (72.8%) met established cutoff criteria for sleep problems on the parent-report Children’s Sleep Habits Questionnaire (CSHQ), though study-specific elevations for specific sleep domains (i.e., subscale mean score ≥2 corresponding to a response of “2–4 times in a typical week”) ranged from 1.5% (sleep-disordered breathing) to 5.8% (sleep duration) (Langberg et al., 2017). In contrast, 28% met study-specific elevations for daytime sleepiness, and 22% similarly had elevated daytime sleepiness per youth self-report (Langberg et al., 2017). Of note, this study did not include a comparison sample of adolescents without ADHD to examine how rates compared to adolescents with ADHD.

One of the largest studies to date was conducted by Chiang et al. (2010) and included 325 adolescents (ages 10–17 years) with ADHD and 257 comparison adolescents without ADHD in Taiwan. Adolescents with ADHD were more likely to have a range of sleep problems/disorders than adolescents without ADHD, with a number of findings specific to certain ADHD subtypes/presentations. Adolescents with ADHD combined type (ADHD-C) or ADHD predominantly inattentive type (ADHD-I) had more insomnia symptoms, sleep terrors, bruxism, and snoring than adolescents without ADHD. Both the ADHD-I and ADHD-C groups also had reported more inadvertent daytime napping, though the ADHD-I group had the highest rates of hypersomnia. Only adolescents with ADHD-C had more circadian rhythm and sleep talking than adolescents without ADHD; adolescents with ADHD-C or ADHD predominantly hyperactive-impulsive type (ADHD-HI) reported having more nightmares. Interestingly, the authors found that ADHD symptoms were associated with earlier bedtimes and longer sleep duration on school days, and the authors note that findings may be in part attributable to the competitive academic demands in Taiwan whereby adolescents with ADHD may be less likely than other adolescents to engage in academic work or attend “cram schools” (Chiang et al., 2010). This possibility underscores the importance of carefully considering cultural and environmental factors that may influence sleep schedules in adolescents with ADHD.

In a population-based sample of almost 10,000 adolescents (ages 16–19 years) in Norway, participants were classified with “high ADHD symptoms” (scoring above the 90th percentile on a self-report ADHD rating scale) or “low ADHD symptoms” (scoring at or below the 90th percentile) (Hysing, Lundervold, Posserud, & Sivertsen, 2016). In contrast to the findings of Chiang et al. (2010), Hysing and colleagues found that participants with high ADHD symptoms reported shorter sleep duration (by approximately 1 hour) and time in bed (by approximately 20 minutes), as well as longer sleep onset latency (SOL) and wake after sleep onset, lower sleep efficiency, greater sleep need and oversleep, and more frequent sleepiness/tiredness during the day than adolescents with low ADHD symptoms. Further, one-third (33.7%) of the high ADHD symptom group met diagnostic criteria for insomnia, a rate three times higher than found in the low ADHD symptom group (11.4%) (Hysing et al., 2016). Adolescents in the high ADHD symptom group were also significantly more likely than adolescents in the low ADHD symptom group to meet operationalized criteria for delayed sleep phase syndrome (7.6% and 2.8%, respectively) (Hysing et al., 2016). In analyses examining the separate ADHD inattention and ADHD hyperactivity–impulsivity dimensions, inattention was generally found to be more clearly associated with sleep disturbances. In separate analyses from the same Norwegian sample, adolescents classified with possible delayed sleep phase had more ADHD symptoms, and inattention symptoms particularly, than adolescents without delayed sleep phase (Sivertsen, Harvey, Pallesen, & Hysing, 2015). Similar findings have been reported in young adults aged 18 years in relation to overall sleep quality (Gregory et al., 2017).

We recently compared the sleep and daytime sleepiness of 302 eighth grade adolescents, with approximately half with ADHD and the other half a comparison sample without ADHD (though other psychiatric disorders were allowed) (Becker, Langberg, Eadeh, Isaacson, & Bourchtein, 2018). Using daily sleep diaries, adolescents with ADHD were more likely than adolescents without ADHD to obtain insufficient sleep on school days and on weekends, have longer school night SOL, and have an earlier school day wake time than adolescents without ADHD. Adolescents with ADHD also had greater sleep problems according to both self and parent report and significantly greater daytime sleepiness across self, parent, and teacher reports. In analyses that controlled for a host of variables known to impact sleep (e.g., sex, pubertal development, medication use, psychiatric comorbidity), ADHD remained associated with shorter school night sleep duration, adolescent- and parent-reported daytime sleepiness, and parent-reported difficulties initiating and maintaining sleep and total sleep disturbance. In fact, controlling for these other variables, the odds of being classified with clinically elevated parent-reported sleep disturbance were 6.20 times greater for adolescents with ADHD (Becker, Langberg, et al., 2018). These findings add to a small but growing body of literature indicating that adolescents with ADHD have more sleep problems and daytime sleepiness than their peers without ADHD.

Few studies have examined actigraphy-measured sleep in adolescents with ADHD (De Crescenzo et al., 2016). Using four nights of actigraphy data and corresponding daily sleep diaries, Mullin, Harvey, and Hinshaw (2011) compared the sleep of 14 adolescents (ages 11–17 years) with ADHD-C to 13 adolescents with bipolar disorder and 21 typically developing adolescents. The adolescents with ADHD-C had the shortest total sleep time across both actigraphy and daily diary, lowest sleep efficiency (per actigraphy), and longest SOL (per diary) of the three groups, though differences were not statistically significant. The authors noted the limited sample size, as well as not accounting for weekend versus weekday sleep, may have contributed to the lack of significant findings in this study, and effect sizes were generally medium between the ADHD and typically developing groups (Mullin et al., 2011). Another study found no links between having an ADHD diagnosis and either total sleep time or sleep time variability (measured with coefficient of variation) in an community-based sample of 247 adolescents (ages 13–16 years), though it is important to note that ADHD was assessed based on parent-report of the adolescent having received a previous diagnosis by a physician (Moore et al., 2011). In our recent study of 302 eighth grade students, few differences were found on actigraphy indices, though adolescents with ADHD did have shorter school nighttime in bed and school day wake time than adolescents without ADHD, and ADHD remained associated with shorter school night sleep duration when controlling for a number of key variables (Becker, Langberg, et al., 2018). Our findings, coupled with the Mullin et al. (2011) study, suggest that adolescents with ADHD may obtain less actigraphy-measured sleep, though additional actigraphy studies in adolescents with and without ADHD are clearly needed.

A series of studies by Prehn-Kristensen and colleagues (Munz et al., 2015; Prehn-Kristensen et al., 2014; Prehn-Kristensen, Göder, et al., 2011; Prehn-Kristensen, Molzow, et al., 2011) used polysomnography (PSG) to examine sleep parameters, memory consolidation, and transcranial direct-current stimulation (a type of neurostimulation using electrodes, in this case bilaterally at frontolateral locations and starting 4 minutes after entering non-rapid eye movement (non-REM) sleep stage 2 and applied during five intervals for 5 minutes each (1 minute between intervals)) in young adolescent males diagnosed with ADHD. In their first study, the investigators examined the impact of sleep on the consolidation of declarative memory (i.e. memory of facts and events that can be recalled) in 12 adolescents (ages 10–16 years) with ADHD and 12 healthy controls (ages 11–14 years). Adolescents with ADHD had longer SOL, lower sleep efficiency, more REM sleep minutes, and shorter SWS latency than controls; no group differences were found for total sleep time, number of awakenings or arousals, sleep stage 1–4 times, or non-REM sleep duration. Further, both non-REM sleep duration and slow oscillation power (0.5–1 Hz) during non-REM sleep were positively associated with sleep-associated declarative memory consolidation (using a picture recognition task) in healthy controls but not in adolescents with ADHD, suggesting “reduced functionality of early night slow oscillations in sleep-associated consolidation of declarative memory in ADHD” (Prehn-Kristensen, Goder et al., 2011, p. 676). Another study of 16 young adolescents with ADHD and 16 controls (ages 9–12 years) found no group differences in PSG-measured sleep parameters (Prehn-Kristensen, Molzow, et al., 2011). However, adolescents with ADHD, but not healthy controls, demonstrated improved procedural memory (using a button-box task) following sleep compared to wakefulness, with REM-density positively correlated with faster reaction times in the ADHD group (Prehn-Kristensen, Molzow, et al., 2011).

Two other studies by the same research group examined effects of slow oscillating transcranial direct-current stimulation during non-REM sleep stage 2 (Munz et al., 2015; Prehn-Kristensen et al., 2014). The first study found transcranial direct-current stimulation to improve declarative memory performance in adolescents (ages 10–14 years) with ADHD to a level comparable to healthy control adolescents (Prehn-Kristensen et al., 2014). Transcranial direct-current stimulation also improved reaction time and reaction time variability on a go/no-go task in 14 young adolescent males (ages 10–14 years) with ADHD, though intrinsic alertness using a simple stimulus response task and motor memory performance using a finger sequence tapping task were not improved, and no control group was included (Munz et al., 2015). Together, this series of studies points to the potential importance of sleep parameters for the memory of adolescents with ADHD, as well as potential utility of transcranial direct-current stimulation for improving memory performance and reaction time/reaction time variability in adolescents with ADHD. As reviewed by Lunsford-Avery et al. (2016), larger-scale studies are needed to better understand whether adolescents with ADHD differ from their peers in PSG-assessed sleep and the extent to which sleep parameters impact neurocognitive and daily life functioning.

The multiple sleep latency test (MSLT) (Carskadon et al., 1986) and maintenance of wakefulness test (MWT) (Mitler, Gujavarty, & Browman, 1982) are objective, lab-based assessments of excessive somnolence and daytime sleepiness/alertness, typically conducted during the day following an overnight PSG. While preparing this chapter, no studies were found that compared daytime alertness between adolescents with and without ADHD using the MWT. Consistent with extant studies showing that adolescents with ADHD have more subjectively measured daytime sleepiness than their peers (Chiang et al., 2010; Hysing et al., 2016), the one study using the MSLT in youth with ADHD that spanned adolescence (M_age=12.4± 4.6 years) found greater daytime sleepiness in the ADHD group as compared to a matched comparison group (Golan, Shahar, Ravid, & Pillar, 2004). However, the age range or number of participants in adolescence were not reported, and the authors noted that “patients’ ages were heterogeneously distributed” (Golan et al., 2004, p. 264). Since puberty is associated with increased daytime sleepiness in adolescence (Carskadon, 1990; Carskadon, Acebo, & Jenni, 2004) and has rarely been considered in studies examining sleep in adolescents with ADHD, there is a clear need for studies that compare objectively measured daytime sleepiness in adolescents with and without ADHD, taking care to consider both chronological age and pubertal status as well as sex.

Adolescents with ADHD have elevated rates of psychiatric comorbidity (Smalley et al., 2007), and there is long-standing interest in the extent to which comorbid symptoms/diagnoses contribute to or exacerbate sleep difficulties in youth with ADHD. One study found that having at least one comorbid psychiatric disorder based on diagnostic interviews conducted with the adolescent and a parent was associated with increased sleep problems (including insomnia and nightmares) in a sample of 281 adolescents (ages 11–17 years) with a childhood diagnosis of ADHD (Gau & Chiang, 2009). Hysing et al. (2016) found that depressive symptoms reduced the associations of ADHD symptoms—particularly inattentive symptoms—in relation to poorer sleep, though ADHD symptoms did remain significantly associated with poorer sleep. Likewise, having an ADHD diagnosis is associated with poorer sleep quality in young adulthood (age 18 years), even after accounting for psychiatric comorbidity including depression which is most strongly associated with sleep quality (Gregory et al., 2017). Both ADHD symptom severity and having comorbid internalizing disorder have also been linked to self-reported difficulties with going to bed and parent-reported sleep problems in adolescents with ADHD (Martin et al., 2018). Studies have found both anxiety disorders (Mick, Biederman, Jetton, & Faraone, 2000) and depressive symptoms (Stein et al., 2002) to be particularly associated with increased sleep problems in adolescent males with ADHD. In considering daytime sleepiness, studies have found that co-occurring sluggish cognitive tempo (SCT) symptoms (e.g., daydreaming, mental confusion, slowed behavior/thinking) are distinct from, yet strongly related to, daytime sleepiness in adolescents and young adults with ADHD (Langberg et al., 2017; Langberg, Becker, Dvorsky, & Luebbe, 2014). Together, these findings suggest that comorbidity and sleep difficulties are linked in adolescents with ADHD, though there is a need for much more research that can better tease apart directionality as well as specificity in both sleep and comorbidities.

Two longitudinal studies have examined sleep and comorbidity in children/early adolescents with ADHD. Lycett, Mensah, Hiscock, & Sciberras (2014) found that having both an internalizing and externalizing comorbidity predicted both transient and persistent parent-rated sleep problems over a 1-year period in 195 children/young adolescents (ages 5–13 years at initial time point, M_age=10.1) with ADHD. In considering the reverse association, Becker, Langberg, and Evans (2015) found parent-reported sleep problems to predict increases in both depressive symptoms and oppositional behaviors over a 1-year period in a sample of 81 young adolescents (ages 10–14 at initial time point, M_age=12.2) with ADHD. Some evidence of specificity with internalizing symptoms was also found, as sleep problems predicted increased depressive symptoms but not anxiety symptoms (Becker et al., 2015). There is a clear need for additional longitudinal studies in this area, including studies of middle and late adolescence and studies that consider other psychopathologies (e.g., autism, substance abuse).

A series of studies by Langberg and colleagues have demonstrated the importance of daytime sleepiness for the academic performance of adolescents with ADHD. First, in a sample of 100 young adolescents (ages 10–14 years) with ADHD, self-reported daytime sleepiness was associated with more parent-reported homework problems and academic impairment, as well as lower teacher-rated academic competence, above and beyond ADHD inattentive symptom severity (Langberg, Dvorsky, Marshall, & Evans, 2013). Daytime sleepiness was not associated with adolescents’ grade point average (GPA) when controlling for inattention severity, and self-reported sleep duration was unassociated with any of the academic variables (Langberg et al., 2013). Similar findings were reported in a sample of 62 university students (M_age=19.5 years) carefully diagnosed with ADHD and assessed at the beginning and end of the academic year: self-reported daytime sleepiness prospectively predicted greater school maladjustment and the number of poor and failing grades, above and beyond both self- and parent-reported ADHD symptoms, but did not predict GPA (Langberg, Dvorsky, Becker, & Molitor, 2014). It is also possible that school difficulties predict subsequent daytime sleepiness. In the same sample of college students, Langberg, Dvorsky, Becker, and Molitor (2016) found school maladjustment at the beginning of the school year to predict greater daytime sleepiness at the end of the school year, controlling for ADHD symptoms and daytime sleepiness at the start of the school year. Further, greater external locus of control mediated the association between school maladjustment and daytime sleepiness, suggesting that college students who believe that events are not in their control may have poor sleep hygiene and/or dampened daytime arousal that contributes to or manifests as excessive daytime sleepiness (Langberg et al., 2016). Additional studies are needed to further investigate developmental processes and mechanisms linking sleep and/or daytime sleepiness to academic functioning and vice versa.

ADHD medication use was associated with higher odds of persistent sleep problems in children and young adolescents diagnosed with ADHD (Lycett et al., 2014). Mick et al. (2000) found stimulant medication use to be associated with restless sleep, night wakings, talking in sleep, and fear of sleeping in the dark in a sample of adolescent males with ADHD. Another study found adolescent males (ages 13–16 years) with ADHD taking methylphenidate had more sleep problems than comparison males and nonmedicated males with ADHD, who did not differ from each other in their sleep problems (Stein et al., 2002). Other studies have not found medication use to be associated with sleep problems or disorders in adolescents with ADHD (Becker et al., 2015; Gau & Chiang, 2009). Of note, adolescents with more severe ADHD are likely to take stimulant medication, and studies reviewed above have been inconsistent in whether they accounted for ADHD symptom severity in analyses and have also relied on broad measures of medication use (e.g., parent-report yes/no), which are important considerations for future research.

Remarkably few studies have examined sleep in adolescents with ADHD. It is thus not entirely clear whether adolescents with ADHD have more sleep problems than their peers (this is especially true for objective measures of sleep) and, if so, what domains of sleep are particularly disturbed in adolescents with ADHD. This is a clear priority for future research that can inform theoretical models of sleep in adolescent ADHD, the sleep domains that best differentiate typically developing peers from teens with ADHD, and possible targets for prevention and intervention efforts. In addition, although girls with ADHD may have more sleep problems than their peers (Becker, Cusick, Sidol, Epstein, & Tamm, 2018), and adolescent females have more sleep problems than adolescent males (Galland et al., 2017; Petrov, Lichstein, & Baldwin, 2014), sex differences have not convincingly emerged in adolescents with ADHD specifically (Gau & Chiang, 2009) though additional studies are certainly needed. Since most studies examining sleep in adolescents with ADHD have been disproportionately male, it is possible that rates of sleep problems will be found to be even higher among studies that include more female participants.

There is ongoing interest in the extent to which sleep difficulties contribute to ADHD itself or exacerbate ADHD symptoms. One study found shorter parent-reported sleep duration in childhood to be associated with greater self-reported attention problems in young adulthood, though other childhood sleep domains were not linked to more attention problems in adulthood and childhood talking/waking during sleep was linked to lower attention problem scores later in adulthood (Gregory, Van der Ende, Willis, & Verhulst, 2008). Considering the converse association, Lycett et al. (2014) found that 10% of youth with ADHD had persistent parent-reported sleep problems over a 1-year period, with ADHD symptom severity (as well as internalizing and externalizing comorbidities) associated with increased odds of persistent sleep problems. In contrast, Hansen, Skirbekk, Oerbeck, Wentzel-Larsen, and Kristensen (2013) found 71% of youth (ages 7–13 years) diagnosed with ADHD to have persistent parent-reported sleep problems on the over an 18-month period. One reason for the stark difference in rates of sleep problem persistence between the Lycett and Hansen studies may be due to how sleep problems were measured: in the Lycett study a single item was used that asked parents to rate the severity of their child’s sleep problems as mild, moderate, or severe, whereas in the Hansen study an established cutoff on the 33-item CSHQ was used. Clearly, additional studies are needed to evaluate sleep problem persistence using different subjective and objective measures of sleep in youth with ADHD, as well as youth self-report of sleep in adolescent-specific samples.

Interestingly, Gregory et al. (2017) recently found that persistent ADHD was linked to poorer sleep quality in young adulthood, hypothesizing that underlying brain vulnerabilities that contribute to the associations between ADHD and sleep quality. In contrast, Gau and Chiang (2009) found that adolescents with a childhood diagnosis of ADHD had more current and lifetime sleep problems/disorders in adolescence regardless of ADHD persistence. These studies used different measures of sleep (overall sleep quality vs sleep disorder symptoms/diagnoses), were conducted in different cultural contexts (England vs Taiwan), and included participants at different developmental levels (adolescence vs young adulthood), making it difficult to tease apart the precise reasons for discrepant findings. In any event, these studies point to the need for additional studies examining how ADHD persistence relates to ongoing sleep problems in adolescence with ADHD.

Studies that seek to untangle the complex associations between sleep and ADHD symptoms are also needed (Cassoff, Wiebe, & Gruber, 2012). Studies with typically developing adolescents have found shortened sleep duration and sleep disturbances (e.g., sleep-disordered breathing) to be associated with ADHD symptoms and inattentive symptoms specifically (Johnson & Roth, 2006). These findings are bolstered by experimental studies that point to inadequate sleep as a causal contributor to poorer attentional functioning in adolescents (Beebe et al., 2008). To extend these findings to a clinical sample, we recently completed an experimental sleep restriction/extension protocol in adolescents (ages 14–17 years) diagnosed with ADHD (Becker, Epstein, et al., 2018). Seventy-two participants were enrolled in a 3-week sleep manipulation protocol using a cross-over experimental design, including a phase stabilization week followed in counterbalanced order by a sleep restriction week (6.5 hours in bed) and a sleep extension week (9.5 hours in bed). Analyses included 48 adolescents who had complete actigraphy data and were adherent to the sleep protocol (defined a priori as obtaining ≥1 hour actigraphy-measured sleep duration during sleep extension compared to sleep restriction). Compared to the extended sleep week, parents reported more inattentive and oppositional symptoms during the restricted sleep week. In addition, both parents and adolescents reported more SCT symptoms, as well as greater daytime sleepiness, during sleep restriction compared to sleep extension, and adolescents reported less hyperactive-impulsive symptoms during the sleep restriction condition. We did not find any effects were found for parent-reported hyperactivity–impulsivity (as hypothesized given research with typically developing adolescents), adolescent-reported ADHD inattention, or continuous performance test variables (Becker, Epstein, et al., 2018). Thus, effects were only found for nonblinded ratings (though not all ratings, bolstering confidence in the study findings), and it would be highly informative to conduct the protocol during the academic year to collect blinded teacher ratings and other measures of daily life impairment. In any event, this study provides key preliminary evidence of shortened sleep duration to be a causal contributor to poorer attentional functioning in adolescents with ADHD, though additional studies will be needed that also include adolescents without ADHD as well as varying degrees of sleep restriction and extension.

As noted earlier, few longitudinal studies have been conducted examining the interrelations of sleep, ADHD, and adjustment in adolescence. Longitudinal studies examining sleep in adolescents with ADHD and associations with diverse functional outcomes is a pressing research priority with clinical implications. In a rare study examining bidirectional associations, Mulraney, Giallo, Lycett, Mensah, and Sciberras (2016) found little evidence for bidirectional associations between sleep problems and internalizing or externalizing difficulties over a 1-year period in a sample of 270 children/young adolescents (ages 5–13 years). As noted by Mulraney et al. (2016), studies may need to extend beyond a 1-year period to uncover developmental processes, and this may be especially important in middle and late adolescence when emotional problems and internalizing symptoms are likely to rise. There is also a need to include other functional outcomes beyond comorbidities. For example, considering the interplay of academic/homework impairment, peer/family relationships, executive functions, and salient developmental facets of adolescence (e.g., driving, romantic relationships, substance/alcohol use, employment) are areas ripe for inquiry. Another important domain is that of technology and media use. Adolescent males (ages 13–15 years) with ADHD report more compulsive Internet use than adolescent males without ADHD (Weinstein et al., 2015). In addition, a study of 81 adolescents (ages 13–17 years) with ADHD found that adolescents obtaining less than the recommended 8 hours of sleep on school nights had more nighttime media use (i.e., after 9:00 p.m.) than adolescents obtaining 8 or more hours of nightly sleep (Becker & Lienesch, 2018). Furthermore, controlling for age, sex, pubertal development, stimulant medication use, and ADHD symptom severity, nighttime media use was associated with both adolescent- and parent-reported shorter sleep duration and increased sleep problems, as well as greater adolescent-reported internalizing symptoms and eveningness circadian preference (Becker & Lienesch, 2018). The cross-sectional design of these studies precludes drawing causal conclusions but nevertheless point to the importance of evaluating technology use and other contextual factors in studies seeking to understand the sleep and daytime functioning of adolescents with ADHD.

There is some indication, primarily from research conducted with school-aged children (Gruber & Sadeh, 2004; Gruber, Sadeh, & Raviv, 2000), that individuals with ADHD have greater intraindividual variability in their sleep/wake patterns compared to individuals without ADHD (Becker, Sidol, Van Dyk, Epstein, & Beebe, 2017). One study finding greater sleep variability in youth with ADHD was conducted in youth spanning childhood and adolescence (ages 6–13 years) (Moreau, Rouleau, & Morin, 2014), though conflicting findings were reported in another study of youth (ages 6–14 years) with ADHD (Owens et al., 2009). Given the distinct context of adolescence, including heightened academic demands, extracurricular activities, increased technology/media use, growing importance of peer relationships, and greater independence over sleep/wake schedules, it is particularly important to examine sleep variability in adolescents specifically. The one study that has done so in adolescents with ADHD found no difference in sleep time variability between adolescents with and without a parent-reported diagnosis of ADHD (Moore et al., 2011). In addition to the limitation of relying on parent-report of ADHD diagnosis, the study only examined sleep time variability and did not consider comorbidities or medication use. Variability in other sleep parameters (e.g., SOL, night wakings) have been reported in the previous studies, and both psychiatric comorbidity and medication use are also relevant when examining sleep variability in youth with ADHD (Becker et al., 2017).

Another area that has yet to receive much empirical attention is the transition from adolescence to young adulthood, including entering into the workforce or attending university. Of course, the transition from childhood to adolescence is also one worthy of additional scrutiny, though far more research has been done in samples spanning childhood and adolescence. The transition to adulthood is also unique in that is the first time for many (if not most) individuals that they are solely responsible for setting their sleep/wake schedules and habits. ADHD is a chronic illness for many (Turgay et al., 2012), persisting into adulthood approximately 50% of the time (Sibley, Mitchell, & Becker, 2016). As described by the ADHD Life Transition Model, it is precisely in late adolescence and early adulthood that environmental demands (e.g., academic, occupational, financial, and social activities and functions) outpace support resources (e.g., external support provided by parents and teachers) (Turgay et al., 2012). As further detailed by Turgay et al. (2012), “As patients grow older and daily academic and social demands become more complex, impairments can result in more serious, longer-term consequences” (p. e3). In line with this possibility, recent findings from the Multimodal Treatment of ADHD (MTA) study found that, compared to non-ADHD peers, participants with ADHD histories had increased impairment both before and after the transition to adulthood (Howard et al., 2016). Of note, impairment stabilized after high school for the 42% of participants with an ADHD history who attended college, though almost half of these participants still experienced some degree of clinically significant impairment (Howard et al., 2016).

What is the relevance of these findings for sleep specifically? Although less is known about young adults who do not attend college (a research priority in and of itself), it is estimated that 60%–65% of college students have poor sleep (Becker, Jarrett, et al., 2018; Lund, Reider, Whiting, & Prichard, 2010). Further, ADHD symptoms are associated with sleep problems among college students (Becker, Jarrett, et al., 2018; Becker, Luebbe, & Langberg, 2014; Gau et al., 2007). As described earlier, Gregory et al. (2017) found that persistent ADHD that was linked to poorer sleep quality in young adulthood, though studies have yet to carefully examine ADHD and sleep across the transition from adolescence to adulthood. Although sleep improves for some students as they enter college, there is evidence that depressive symptoms before the transition to college may be a risk factor for worsening sleep problems in college (Doane, Gress-Smith, & Breitenstein, 2015). It is unknown whether ADHD similarly predicts poorer sleep across the transition to college. Further, other studies have found sleep quality to be bidirectionally associated with improved social ties, emotion dysregulation (Tavernier & Willoughby, 2015), and intrapersonal adjustment (including depression, self-esteem, and daily hassles) throughout college (Tavernier & Willoughby, 2014). Better friendship quality and higher academic achievement also predict improved sleep quality over time (Tavernier & Willoughby, 2014), and there is some evidence that friendship may be a particularly important buffer during the transition to university for students with high ADHD symptoms (Khalis, Mikami, & Hudec, 2017). Another study found longer sleep duration and reduced sleep variability to be key factors in first-year students experiencing improved adjustment from the first to the second semester of college (Ari & Shulman, 2012). The authors concluded that “counselors and students should take sleep into consideration when they discuss and try to understand costs and the processes of the transition to the college environment” (p. 287). This may be especially important for students with ADHD and studies are needed that examine the role of sleep as adolescents with ADHD transition to university or the workforce. It will be important for such studies to measure sleep and adjustment before the transition to adulthood, consider characteristics of the work environment (e.g., job security, night or rotating shift work) and educational setting (e.g., vocational school, 2-year college, 4-year college), and evaluate the extent to which bidirectional associations are distinct for individuals with ADHD.

Two studies with samples including children and adolescents with ADHD have found support for melatonin in improving sleep (Van Der Heijden, Smits, Van Someren, Ridderinkhof, & Gunning, 2007; Weiss, Wasdell, Bomben, Rea, & Freeman, 2006). Weiss and colleagues found longer parent-reported sleep duration and shorter parent-reported and actigraphy-measured SOL when youth (ages 6–14 years) were taking melatonin (5 mg administered 20 minutes before bedtime) compared to placebo, even after a sleep hygiene intervention had been completed. In youth (ages 6–12 years) with both ADHD and sleep onset insomnia, Van Der Heijden et al. (2007) also found shorter SOL, advanced dim light melatonin onset, less nocturnal restlessness, and increased sleep efficiency and total sleep time with melatonin (3–6 mg depending on body weight, administered at 7:00 p.m.) compared to placebo. Importantly, in a naturalistic follow-up study, 65% of participants continued to take melatonin 3.7 years later (when most participants were in adolescence) and demonstrated improvements in sleep as well as behavior and mood problems, with discontinuation associated with a sleep onset delay in most children (Hoebert, Smits, & Van der Heijden, 2008). Of note, in both trials (Van Der Heijden et al., 2007; Weiss et al., 2006), improved sleep did not correspond with improved behavior, cognition, or ADHD symptoms, suggesting that ADHD is itself not simply attributable to sleep problems (though it should also be noted that the studies were not designed to test this question). There is limited evidence for other pharmacological treatments improving sleep in youth with ADHD (Cortese et al., 2013), and no studies have been conducted in adolescents with ADHD specifically.

In providing recommendations for managing sleep problems in youth with ADHD, Cortese et al. (2013) determined that “behavioral interventions should be considered a first-line treatment of insomnia, although further evidence from randomized controlled trials (RCTs) is needed to prove their efficacy in ADHD” (p. 784). This is certainly true for adolescents with ADHD, a population for which very few studies have evaluated behavioral sleep interventions. In the melatonin study by Weiss and colleagues described earlier, a sleep hygiene intervention was given for 10 days prior to entering the cross-over melatonin trial (Weiss et al., 2006). From baseline to postsleep hygiene, SOL was reduced based on both parent-reported sleep diary (91.7 and 69.3 minutes, respectively) and actigraphy (98.1 and 73.0 minutes, respectively). SOL variability was also reduced following the sleep hygiene intervention, and clinicians rated 42% of participants as at least minimally improved. Further, 17.9% of the sample met study criteria for response to the sleep hygiene intervention (defined as a sleep latency <1 hour) and did not continue with the melatonin phase of the study. However, 54% of participants were rated by clinicians as having no change following the sleep hygiene intervention and 4% were rated as minimally worse. While promising, findings indicate much more remains to be done to determine how to best improve sleep in youth with ADHD using behavioral interventions, though it is important to note that the Weiss et al. study used low-intensity sleep hygiene intervention over a very short time period and focused almost entirely on SOL and onset variability. More comprehensive behavioral interventions have recently been developed and tested in school-aged children (with some participants in the adolescent age range), with promising results (Corkum et al., 2016; Hiscock et al., 2015; Keshavarzi et al., 2014; Sciberras, Fulton, Efron, Oberklaid, & Hiscock, 2011). However, these interventions are primarily delivered to parents and will likely need modifications for use with adolescents with ADHD, both because of the increased autonomy in adolescence generally and the unique impairments frequently experienced by adolescents with ADHD.

A mixed methods study by Bussing et al. (2016) is illuminating in considering some of the unique challenges likely to arise when implementing a behavioral sleep intervention with adolescents with ADHD. The investigators examined willingness to use ADHD self-management strategies in adolescents (ages 14–19 years) who were classified in childhood with being at high or low risk for ADHD. Sleep regulation strategies fell at the bottom of acceptable self-management interventions for high-risk adolescents and their parents. As described by the authors, “parents anticipated that forcing specific bedtimes on their teenagers would create too many conflicts, and thought it might work against adolescents’ biorhythms. Adolescents, in turn, noted that earlier bedtimes could cause insomnia and would make them feel treated like a child” (p. 566). As such, sleep regulation was also perceived as an intervention that would lead to relationship conflicts. Since sleep self-management strategies “stood out as particularly unpopular among adolescents with high ADHD risk” (p. 571), the authors further suggested that sleep intervention development efforts should particularly consider developmental factors, including biorhythms, concerns surrounding iatrogenic insomnia, and feeling treated like a child, so interventions can be optimized for both acceptability and effectiveness for both parents and adolescents (Bussing et al., 2016).

These considerations will be important for efforts to either upwardly extend interventions for children with ADHD to adolescents with ADHD or to test existing cognitive–behavioral interventions developed for adolescents for use in adolescents with ADHD who also have sleep problems. In terms of the latter, there is growing evidence supporting cognitive–behavioral therapy for insomnia (CBT-I) in adolescents with sleep problems (Blake, Sheeber, Youssef, Raniti, & Allen, 2017), though none have been tested in adolescents with ADHD who have co-occurring sleep problems. As mentioned earlier, sleep is increasingly considered a transdiagnostic mechanism contributing to both mental disorders and their impairments (Harvey et al., 2011), which has led to a shift away from disorder-specific sleep interventions in an effort to streamline efforts and effectiveness using a transdiagnostic approach, as exemplified in the Transdiagnostic Sleep and Circadian (TranS-C) intervention (Harvey & Buysse, 2018; Harvey, 2016). Yet, this transdiagnostic approach has yet to be tested across adolescents with heterogeneous psychiatric disorders, including ADHD. Although general treatment principles and components may be effective with adolescents with ADHD, some considerations may also be important to optimize this and similar interventions for adolescents with ADHD. A summary of the TranS-C youth intervention modules is provided in Table 11.1, including possible considerations for implementing the intervention with adolescents with ADHD. As can be seen, many of the considerations for working with adolescents with ADHD relate to the behaviors often inherent to the disorder (e.g., forgetfulness, poor organization, and time management), as well as associated impairments (e.g., homework/school problems, co-occurring mental health symptoms) and sleep-specific factors (e.g., intraindividual variability). It will also be crucial to determine at the start of treatment the extent to which the adolescent views their current sleep as problematic or whether someone else (e.g., parent) views the sleep as problematic and has initiated treatment (McDonagh & Bateman, 2012). Other considerations that are likely to be relevant when working with adolescents with ADHD are provided in Table 11.1. It should be noted that while the TranS-C intervention is used here as an exemplar intervention, TranS-C is based on other evidence-based interventions that may themselves be useful with the same considerations for working with adolescents with ADHD. The key here is that there is a pressing need for intervention development and evaluation research to address the sleep problems in adolescents with ADHD.

Table 11.1

Transdiagnostic sleep and circadian for youth (TranS-C youth) intervention modules and considerations for adolescents with ADHD

Module	Purpose	Considerations for adolescents with ADHD
Functional analysis	Derive treatment targets. Introduce the rationale for treatment.	For adolescents with ADHD, functional analysis will be important to understand sleep (and specific sleep domains) on core ADHD symptoms and associated impairments. The daily sleep diary is a key aspect of the functional analysis and deriving treatment targets. Adolescents with ADHD may need a reminder system (e.g., alarm, note on bathroom mirror, text/phone call from therapist’s office) to complete the sleep diary each day. It will also be important early on to determine the extent to which parents will be involved in treatment; some parent involvement is likely helpful if done in a supportive manner that does not increase parent–adolescent conflict and the adolescent maintains investment and ownership of the intervention goals and progress.
Sleep and circadian education	Provides the rationale for the treatment modules and home projects.	Adolescents with ADHD may have a later circadian preference than adolescents without ADHD. It may also be useful to review any medications taken and their potential impact on sleep, with consultation with the prescribing physician likely important in some situations.
Motivational interviewing	Heightens motivation to modify behavior.	Motivational interviewing may be especially important for adolescents with ADHD, particularly if the adolescent does not view their sleep as problematic or detrimental to their functioning. It is crucial to find salient motivators for adolescents with ADHD (e.g., becoming a better athlete, doing better at school, having fewer arguments with parents, being allowed to play video games earlier in the day). Motivational interviewing has been successfully used to engage adolescents with ADHD and their parents in other treatments and can likely also be effective for sleep interventions.
Goal setting	Setting realistic, achievable, and measurable goals for the night and the day guides treatment.	Adolescents with ADHD may have difficulty setting realistic goals or underestimate challenges and barriers to achieve goals. Adolescents with ADHD may also be prone to prioritizing short-term goals over long-term goals. Motivational interviewing will remain important when identifying and setting goals, while also acknowledging the likelihood of setbacks throughout treatment. It is also important to be clear about what goals the adolescent has for their own sleep, as well as any goals other people in the adolescent’s life (e.g., parents) have.
Irregular sleep–wake times	Regularize bed and wake times across the week.	Adolescents with ADHD may have particularly irregular sleep patterns and it will be important to understand reasons for irregularity. For example, adolescents with ADHD may procrastinate in completing nightly homework or a long-term project, resulting in both frustration/agitation and late bedtimes.
Difficulty winding down	Supports regularizing bedtimes.	Adolescents with ADHD may have excessive Internet use or video gaming, and nighttime media use is associated with poorer sleep and increased internalizing symptoms in adolescents with ADHD. It may be challenging to identify nontechnological ways of winding down, making this an important area for motivational interviewing and using a harm reduction approach (e.g., 30 min of playing video games is better than 3 h of video games).
Difficulty waking up	Activity scheduling and goal setting to reinforce getting out of bed and help regularize wake-up time.	Youth with ADHD frequently have early morning difficulties as well as high rates of daytime sleepiness. It will be important to explore underlying reasons for having difficulty waking (e.g., disliking school, co-occurring depressive symptoms).
Daytime impairment	Develop skills to cope the day following a night of poor sleep.	Adolescents with ADHD frequently experience a range of daytime impairments, including academic difficulties and social problems. Conducting experiments to determine when these impairments are and are not linked to prior night’s sleep will be valuable.
Unhelpful beliefs about sleep	Correct unhelpful beliefs.	Youth with ADHD are prone to have overly positive beliefs (i.e., positive illusory bias). Though this likely declines by adolescence, some unhelpful beliefs may still emerge in adolescents with ADHD (e.g., “Getting just a little sleep doesn’t affect me like it does other people”).
Poor sleep efficiencya	Associate the bed with sleep.	The principle of going to bed only when sleepy must be balanced with the clinical insights gained and adolescent progress in the modules on irregular sleep–wake times and difficulty winding down, likely needing to revisit issues surrounding homework, technology, and bright lights. As napping can interfere with nighttime sleep efficiency (by discharging homeostatic pressure to sleep), and adolescents with ADHD may be prone to napping more than their peers, assessing and monitoring napping is important.
Too much time in beda	Helps clients who sleep too much get out of bed and more fully engage with their daytime activities.	This module may be especially important for adolescents with ADHD who are using too much time in bed for avoidance (e.g., avoiding going to school) or have co-occurring depressive symptoms. Functional analysis remains important here, and assessing depression and other mood problems will be important throughout treatment.
Delayed phasea	To help clients go to bed early enough to ensure sufficient sleep prior to wake-up time.	As with other modules in this intervention, it is likely that adolescents with ADHD will be able during treatment sessions to create a plan and generate solutions for bedtime and wake time goals. It will likely be more challenging them to follow through and enact the plan on a daily basis. Planning for disruptions to the original plan, as well as setbacks, can further engage the adolescent while providing both support and realistic expectations.
Sleep-related worry	To reduce anxiety and presleep arousal as these are antithetical to sleep.	This module may be especially important for adolescents with ADHD who have co-occurring anxiety. Assessing anxiety and sleep-related cognitions will be important throughout treatment.
Maintenance of behavior change	Relapse prevention and preparing for setbacks.	It is well established that behavioral interventions for youth with ADHD often lose or dampen their impact after implementation ends. Preparing for setbacks will be very important. Gradual termination (moving sessions from weekly to biweekly to monthly) may be helpful, as well as periodic booster session (especially around transition points, such as when starting a new academic year or moving away for university).

ADHD, Attention deficit hyperactivity disorder.

^aDecision to use module is based on daily sleep diary data.

Source: Adapted from Harvey (2016).

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