A systematic review of circadian function, chronotype and chronotherapy in attention deficit hyperactivity disorder

Abstract

Reports of sleep disturbances in attention deficit hyperactivity disorder (ADHD) are common in both children and adults; however, the aetiology of such disturbances is poorly understood. One potentially important mechanism which may be implicated in disrupted sleep in ADHD is the circadian clock, a known key regulator of the sleep/wake cycle. In this systematic review, we analyse the evidence for circadian rhythm changes associated with ADHD, as well as assessing evidence for therapeutic approaches involving the circadian clock in ADHD. We identify 62 relevant studies involving a total of 4462 ADHD patients. We find consistent evidence indicating that ADHD is associated with more eveningness/later chronotype and with phase delay of circadian phase markers such as dim light melatonin onset and delayed sleep onset. We find that there is evidence that melatonin treatment may be efficacious in addressing ADHD-related sleep problems, although there are few studies to date addressing other chronotherapeutic approaches in ADHD. There are only a small number of genetic association studies which report linkages between polymorphisms in circadian clock genes and ADHD symptoms. In conclusion, we find that there is consistent evidence for circadian rhythm disruption in ADHD and that such disruption may present a therapeutic target that future ADHD research might concentrate explicitly on.

The second edge of ADHD: an advantage in motor learning and performance with task-irrelevant background vibratory noise

“…Eveningness and sleep problems are common in adults with ADHD 31 . However, the actigraphy data showed that in the current study the participants of the ADHD and the Cont groups had, overall, similar sleep profiles in the post-training night, except for the tendency of the ADHD participants to have longer sleep latency periods.…”

“…This is an increasingly common finding in young adults and adolescents, attributed to the use of light-emitting devices at evening hours 54 . We also tested for a possible relationship between the participants’ chronotype and their learning abilities, given that training and testing took place in the morning hours 31 . Evening oriented participants are more likely to show lower arousal levels and lower cognitive performance 55 during the morning hours compared to morning-oriented peers, and we conjectured that this may lead to a less engaging learning experience and subsequently to the expression of smaller delayed gains in performance.…”

“…One line of evidence suggests that some of the relative learning deficits in persons with ADHD, could be corrected when training was shortened 1,2,6,30 presumably decreasing the burden of long repetitive practice on mechanisms of sustained attention 8 . An additional line of evidence indicates that motor training scheduled to evening hours can enhance off-line memory consolidation (the expression of delayed learning gains) in young adults with ADHD and close their learning gaps vis-à-vis typically developing adults 10 ; presumably because evening hours are the optimum performance hours for evening-type individuals, a chronotype characterizing many of the individuals with ADHD 31 . It was also shown that five minutes of vigorous physical activity improve affect and executive functioning of children with symptoms of ADHD 32 .…”

Clocks in the clinic: circadian rhythms in health and disease

“…From a mechanistic perspective, a number of cellular and molecular processes have been identified to interact with the clock and modulate mood, including hypothalamic-pituitary-adrenal axis function, immune and neuroimmune processes, neurogenesis and direct control of neurotransmitter and neuromodulator systems 62. Circadian changes have also been described in a number of other psychiatric conditions, including schizophrenia,63 attention deficit hyperactivity disorder,64 obsessive compulsive disorder65 and borderline personality disorder 66. As such, circadian processes appear to be important transdiagnostic factors to consider in psychiatry and clinical psychology.…”

Cross-disorder genetic analyses implicate dopaminergic signaling as a biological link between Attention-Deficit/Hyperactivity Disorder and obesity measures

“…eveningness) and disturbances (e.g. sleep problems) have been repeatedly associated with ADHD and/or ADHD symptoms [25]. These problems have also been linked to BMI variation and obesity.…”