**4. Sleep disorders**

#### **4.1 Insomnia**

Chronic sleep onset insomnia (SOI) is a frequent finding in ADHD children (Mick et al., 2000; Smedje et al., 2001; Corkum et al., 2001; Owens et al., 2000a; O'Brien et al., 2003a) with a prevalence rate of nearly 28% in unmedicated children (Corkum et al., 1999), almost double than the corresponding rate in the normal child population (Owens et al., 2000b; Meijer et al., 2000). Its daytime sequelae heavily impact the cognitive domain of children and, specific to this age group, also behavioral attitude and social conduct. Hyperactivity in fact, rather than overt EDS, is the general marker of insufficient sleep in most children, therefore aggravating the typical features of ADHD (Wiggs & Stores, 1999).

SOI in ADHD was demonstrated to co-occur with a delayed dim-light melatonin onset and sleep-wake circadian rhythm, whereas sleep continuity proved unaffected (Van der Heijden et al., 2005). These findings suggest a possible disturbance of the circadian pacemaker which, in turn, would be due to the alteration of clock genes (Archer et al., 2001), but no clear evidence has been found to confirm this assumption. Sleep hygiene habits of unmedicated ADHD children with SOI were later compared to those of ADHD subjects without insomnia, so as to ascertain whether poor sleep hygiene could at least partially explain insomnia in the affected group (Van der Heijden et al., 2006). The negative results of this study suggest that sleep hygiene practice is not related to sleep characteristics in ADHD children and does not differ significantly whether or not children complain of insomnia.

As early as 1991, Dahl et al. submitted a 10-year-old girl with ADHD and a long-standing SOI to chronotherapy, obtaining a significant improvement of the ADHD-related symptoms along with circadian sleep-phase advancement.

spontaneous or event-related arousals in their subjects' PSG (Silvestri et al., 2009; O'Brien et al., 2003a), arousals have mostly not been formally identified or reported in ADHD PSG studies. Rather, an increased number of phase shifts has been reported (Miano et al., 2006)

The only dedicated paper in terms of a formal approach to explore the microstructural aspects of sleep in ADHD has been written by Miano et al. (2006) who analyzed the cyclic alternating pattern (CAP) in ADHD children without abnormal AHI or PLMs index. The authors reported an overall reduction of CAP rate, an index of sleep instability, in comparison to normal controls, with ongoing reduction of CAP sequences and A1 index, reflecting hypersynchronous delta waves with a protective effect on sleep continuity. This paper would then reconcile the increased fragmentation and low efficiency seen by other authors in ADHD sleep, with the relative compensatory increase of A2 and A3 subtypes,

A striking CAP similarity between ADHD and narcolepsy (Ferri et al., 2005) has been observed along with increased daytime somnolence on multiple sleep latency tests (MSLT). The latter observation is of seminal importance for the interpretation of ADHD as a primary disorder of vigilance (Weinberg & Brumback, 1990). A deficit of the arousal level fluctuations would underlie the concept and clinical considerations which tend to interpret ADHD as "a hypoarousal state" despite its contradictory daytime paradoxical hyperactivity. Further detailing of this theory and related studies are to follow in the sleep disorders

Chronic sleep onset insomnia (SOI) is a frequent finding in ADHD children (Mick et al., 2000; Smedje et al., 2001; Corkum et al., 2001; Owens et al., 2000a; O'Brien et al., 2003a) with a prevalence rate of nearly 28% in unmedicated children (Corkum et al., 1999), almost double than the corresponding rate in the normal child population (Owens et al., 2000b; Meijer et al., 2000). Its daytime sequelae heavily impact the cognitive domain of children and, specific to this age group, also behavioral attitude and social conduct. Hyperactivity in fact, rather than overt EDS, is the general marker of insufficient sleep in most children,

SOI in ADHD was demonstrated to co-occur with a delayed dim-light melatonin onset and sleep-wake circadian rhythm, whereas sleep continuity proved unaffected (Van der Heijden et al., 2005). These findings suggest a possible disturbance of the circadian pacemaker which, in turn, would be due to the alteration of clock genes (Archer et al., 2001), but no clear evidence has been found to confirm this assumption. Sleep hygiene habits of unmedicated ADHD children with SOI were later compared to those of ADHD subjects without insomnia, so as to ascertain whether poor sleep hygiene could at least partially explain insomnia in the affected group (Van der Heijden et al., 2006). The negative results of this study suggest that sleep hygiene practice is not related to sleep characteristics in ADHD children and does not differ significantly whether or not children complain of insomnia. As early as 1991, Dahl et al. submitted a 10-year-old girl with ADHD and a long-standing SOI to chronotherapy, obtaining a significant improvement of the ADHD-related symptoms

therefore aggravating the typical features of ADHD (Wiggs & Stores, 1999).

along with circadian sleep-phase advancement.

with the same clinical significance.

expressing sleep discontinuity.

section under "Narcolepsy".

**4. Sleep disorders** 

**4.1 Insomnia** 

Subsequently, Ryback et al. (2006) confirmed these results in 29 ADHD adults with an open trial of bright-light therapy in the morning.

Interestingly, the reverse relationship does not appear to occur since ADHD symptoms are not commonly found in DSP. Therefore one might assume that SOI per se, as typical of DSP, is not enough to produce daytime feature of ADHD unless accompanied by nighttime hyperactivity/sleep fragmentation, as in most ADHD children (Walters et al., 2008).

As for sleep maintenance insomnia (SMI), several primary sleep disorders such as obstructive sleep apnea syndrome (OSAS), periodic leg movement disorder (PLMD), and restless legs syndrome (RLS) concur in increasing wakefulness after sleep onset (WASO) with night-time awakenings and lowering sleep efficiency with related detrimental effects on performance (Gruber et al., 2007).

These aspects will be developed later on in the course of this chapter, within their respective sections.

Early morning insomnia is not typical of children with ADHD, unless severely depressed and is described only in older groups of ADHD patients.
