Low daytime light and bright night-time light are associated with psychiatric disorders: an objective light study in >85,000 UK Biobank participants

Abstract

Circadian rhythm disturbance is a common feature of psychiatric disorders. Light is the primary input to the circadian clock, with daytime light exposure strengthening rhythms and nighttime light exposure weakening rhythms. However, the independent effects of day and night light exposure on psychiatric outcomes have not been well characterized. In this study, we performed the largest to-date cross-sectional analysis of objectively measured day and night light exposure and examined their relationship with psychiatric disorders. UK Biobank cohort participants aged 37-73 years were recruited into the UK Biobank general cohort population. In a subset of participants (n=86,772; 43% male), light and physical activity patterns were monitored for ~7 days. Using regression models adjusted for age, sex, ethnicity, photoperiod (day length), employment, and physical activity, we examined the independent associations of day and night-time light with psychiatric disorders and measures of symptom severity. We found that greater night light exposure was associated with greater odds of major depressive disorder (MDD), generalized anxiety disorder (GAD), bipolar disorder, post-traumatic stress disorder (PTSD), self-harm behavior and psychotic experiences. Conversely, greater daytime light exposure was associated with lower odds of MDD, PTSD, self-harm behavior and psychotic experiences. There was no significant association of day light exposure with GAD or bipolar disorder. Our findings demonstrate that low day light and bright night light exposure are associated with a wide range of psychiatric outcomes. Avoiding light at night and seeking light during the day may be a simple and effective, non-pharmacological means of broadly improving mental health.

Associations between light exposure and sleep timing and sleepiness while awake in a sample of UK adults in everyday life

“…Our data indicate that even in this population lacking common lifestyles causes of ‘circadian challenge’ (night shift work or jetlag), low daytime and high night-time light exposure are common. Such light exposure patterns are potential causes of circadian and sleep disruptions ( 1 , 5 – 7 , 33 ), with links to several physical and mental health disorders, cognitive dysfunction, occupational well-being and performance, educational attainments, and accidents ( 8 – 15 ).…”

“…To address this knowledge gap, it is necessary to collect data on light exposure and sleep and sleepiness in human populations carrying out their ordinary lives in longitudinal studies. Relationships between wake-time light exposure and sleep timing have indeed been reported ( 10 , 12 , 25 – 28 ). However, these datasets are far from complete.…”

“…Light is the principal synchronizer of daily rhythms in behavior and physiology to external time ( 1 ) and has a direct impact on sleep propensity and sleepiness ( 2 – 4 ). Modern lifestyles impose deviations from natural patterns of light exposure (dimmer daytimes and, especially, brighter nights), with the potential to disrupt circadian rhythms and sleep, and impair performance, health, and well-being ( 5 – 16 ). There is therefore an urgent and ongoing need to determine the extent to which aberrant light exposure impacts sleep and circadian biology in human populations and to devise effective countermeasures.…”

Light–Dark and Activity Rhythm Therapy (L-DART) to Improve Sleep in People with Schizophrenia Spectrum Disorders: A Single-Group Mixed Methods Study of Feasibility, Acceptability and Adherence

“…However, outcomes measures, qualitative accounts, and adverse effects records are promising. There is a substantial existing evidence base supporting various of the components included, such as time in bed restriction and sleep scheduling [38,44], and the positive and negative health impacts of different patterns of light exposure [27,[45][46][47][48]. Furthermore, behavioural sleep interventions with some overlapping components have shown promising results in mixed psychiatric inpatients [49], outpatients [50], participants with persistent delusions and hallucinations [51], and young people at high risk for psychosis [52].…”

“…Changes to light exposure patterns directly affect alertness [20,21], alter circadian entrainment and phase [22,23], and affect mood [24][25][26]. Large-scale Biobank work suggests increased light at night is particularly associated with poorer psychiatric outcomes [27]. There is significant background evidence to suggest which changes are likely to be helpful, but there has been limited work applying advice and behaviour change techniques to support people in altering their own light exposure in the community and then measuring adherence and acceptability.…”