Bright light therapy – circadian treatment

Alterations in the circadian system are driven by CLOCK genes and their interaction with external ‘zeitgebers’ such as light, food intake, and physical activity/exercise. Circadian rhythms and solar intensity as the most important external ‘zeitgeber’, sleep, and CLOCK genes form another pathophysiological link between ADHD and its comorbidities: disturbed circadian rhythm and altered sleep are key features of ADHD. CLOCK genes regulate weight changes, and obesity in turn alters the circadian expression of CLOCK genes. The importance of altered circadian rhythms in mood disorders is also well established, and there is a close link between circadian CLOCKs and mood-related behaviour. Finally, SUDs have been linked to the circadian system. Insight into the alterations of circadian rhythms in ADHD and their relation to comorbid disorders thus opens up the perspective of novel therapeutic modulation of biological systems.

Against the background of substantial circadian rhythm (CIRCA) dysfunction in children and adults with ADHD, only one initial study has examined the potential of chronotherapeutic approaches – i.e. bright light therapy (BLT) – in ADHD. Three weeks of morning BLT advanced the circadian phase in 29 ADHD adults and let to significant reductions in both subjective and objective measures of ADHD symptoms. However, this study has not been replicated at all and using objective biomarkers of circadian phase. Taken together, chronobiological therapies bear substantial innovation potential, but have not yet been systematically tested in ADHD and its comorbidities within a precision medicine framework.

Chronobiological therapies bear substantial innovation potential, but have not yet been systematically tested in ADHD and its comorbidities within a precision medicine framework