Salivary Melatonin Rhythm as a Marker of the Circadian System in Healthy Children and Those With Attention-Deficit/Hyperactivity Disorder

Abstract

Attention-deficit/hyperactivity disorder (ADHD) is the most common neurobehavioral disorder of childhood. Problems with sleep structure, efficiency, and timing have been reported in some, but not all, studies on ADHD children. As the sleep-wake cycle belongs to circadian rhythms, the timekeeping circadian system might be involved in ADHD. To assess whether the circadian system of ADHD children differs from that of controls, the rhythm of the pineal hormone melatonin was used as a reliable marker of the system. Saliva from 34 ADHD and 43 control 6- to 12-yr-old children was sampled at 2-h intervals throughout the entire 24-h cycle, and the melatonin profiles of the ADHD and control children were compared. The nocturnal melatonin peaks of the ADHD and control group did not differ significantly. The high nocturnal interindividual variability of the peaks seen in adulthood was present already in the studied children. The 24-h melatonin profiles of all the ADHD subjects did not differ significantly from those of the control subjects. Categorization of subjects according to age, into groups of 6- to 7-yr-old (9 ADHD, 5 control), 8- to 9-yr-old (16 ADHD, 26 control), and 10- to 12-yr-old (9 ADHD, 12 control) children, revealed significant differences between the ADHD and control group in the melatonin rhythm waveform, but not in nocturnal melatonin peaks; the peaks were about the same in both groups and did not change significantly with increasing age. In the oldest, but not in the younger, children, the melatonin signal duration in the ADHD group was shorter than in the control group. The difference might be due to the fact that whereas in the control group both the evening melatonin onset and the morning offset phase delayed in the oldest children relative to those in the youngest children, in the ADHD group only the onset, but not the offset, phase delayed with increasing age. The data may indicate subtle differences between the circadian system of ADHD and control children during development.

Altered circadian profiles in attention-deficit/hyperactivity disorder: An integrative review and theoretical framework for future studies

“…Two studies have examined endogenous melatonin rhythms in children with ADHD and there is one study in adults (see also Table 2). Compared to control subjects, Nováková et al (2011) did not report different 24-h melatonin profiles in their group of children with ADHD (6-12y). However, when considering younger and older subgroups separately, subtle developmental differences were revealed: i.e., in the oldest children with ADHD (10-12 y) only the onset, but not the offset, phase delayed with increasing age.…”

Methylphenidate Modifies the Motion of the Circadian Clock

“…These symptoms affect a large proportion of adults with ADHD, with 65% complaining of always having trouble sleeping and 87% reporting difficulty going to bed on time (Boonstra et al, 2007). When examining the subset of ADHD patients with sleep-onset insomnia, additional symptoms are observed, most notably delayed onset and offset of sleep, delayed dim-light melatonin onset, and an attenuated amplitude of the rest-activity cycle (Novakova et al, 2011;Van Veen et al, 2010), all symptoms consistent with a disruption of the circadian clock. Supporting this is the recent observation that a polymorphism associated with the gene clock, one of the molecular 'gears' of the intracellular circadian clock, may be a contributing factor for adult ADHD (Kissling et al, 2008).…”

Human Chronotype Is Determined in Bodily Cells Under Real-Life Conditions

“…A direct double-antibody radioimmunoassay was used for the melatonin assay (Bühlmann Laboratories, Allschwil, Switzerland) as previously described (Nováková et al, 2011). The kit was used according to the manufacturer's instructions.…”