A Randomised Controlled Trial of Bright Light Therapy and Physical Activity for Delayed Sleep-Wake Phase Disorder in Adolescents

Author: Cele Richardson

Richardson, Cele, 2018 A Randomised Controlled Trial of Bright Light Therapy and Physical Activity for Delayed Sleep-Wake Phase Disorder in Adolescents, Flinders University, School of Psychology

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There is a widespread and consistent tendency for sleep timing to delay during adolescence. This places adolescents at risk of curtailed sleep duration and a plethora of negative daytime consequences. A more pronounced delay in sleep and circadian timing can lead to Delayed Sleep-Wake Phase Disorder (DSWPD). Given that adolescents’ susceptibility to DSWPD was first reported over 20 years ago, it is surprising only three randomised controlled trials (RCTs) have investigated treatment for adolescent DSWPD, to date. This thesis aimed to address this research priority.

An overview of the empirical literature (Chapter 1) highlighted the need to further investigate the utility of bright light therapy for adolescent DSWPD. The recent development of portable short wavelength light emitting glasses (Re-Timer) allows for the inclusion of adjunct behavioural interventions, which may enhance treatment efficacy. A literature review suggested that scheduled physical activity may facilitate phase advances in circadian and sleep timing (Chapter 2). Therefore, a RCT evaluated the efficacy of bright light therapy and scheduled morning activity for the treatment of adolescent DSWPD. In particular, adolescents received either short wavelength (i.e., green, ~500nm) bright light therapy or long wavelength (i.e., red, ~640nm, placebo) light therapy and physical activity (i.e., interactive video gaming) or sedentary activity (i.e., sitting watching TV, control).

Results from the RCT added to existing literature supporting the use of bright light therapy for DSWPD, with adolescents reporting earlier sleep timing (i.e., sleep onset time, wake-up time), reduced sleep onset latency, increased total sleep time and improved daytime functioning (i.e., daytime sleepiness, fatigue, functional impairment) across treatment and follow-up (Chapter 4). However, treatment outcomes did not differ based on the wavelength of light or morning activity administered. Posteriori analyses revealed the manipulation attempted in the RCT did not result in an objective increase in physical activity. Therefore, it is unclear from this thesis whether physical activity can supplement bright light therapy for adolescents with DSWPD.

DSWPD has been linked with adverse academic outcomes, which may be driven by impaired cognitive performance. Results from the RCT highlighted significant improvements in processing speed and some measures of working memory across treatment and follow-up (Chapter 5). However, it is unclear how clinically meaningful these improvements were, given a comparison with good-sleeping adolescents revealed a lack of statistically significant between-group differences in cognitive performance pre-treatment.

Researchers have called for further research investigating the aetiology of DSWPD and a review of the literature summarised emerging evidence for the role that cognitive “insomnia” processes may play in the development and maintenance of DSWPD (Chapter 3). Chapter 6 provided the first systematic evidence of such processes. Adolescents with DSWPD reported more repetitive negative thinking, physiological arousal, selective attention, sleep-onset misperception and safety behaviours, compared to good-sleeping adolescents. Most cognitive “insomnia” processes reduced alongside chronobiological treatment. However, it is possible that residual “insomnia” symptoms increased the risk of long-term relapse and therefore, further investigation in warranted.

The theoretical and clinical implications of these findings are discussed in Chapter 7, alongside avenues for future research.

Keywords: Delayed Sleep Phase Disorder, Treatment, Light Therapy, Exercise, Adolescence.

Subject: Psychology thesis

Thesis type: Doctor of Philosophy
Completed: 2018
School: School of Psychology
Supervisor: Professor Michael Gradisar