Embrace the dark and ban indoor light pollution

There is growing evidence of a link between patterns of light exposure and mental health outcomes. While you may not be in charge of the lighting in the office, you can take control of the conditions at home.

Evening light levels in the average home are high enough to suppress melatonin by up to 50%. But those effects vary widely depending on our personal profile - Evening home lighting adversely impacts the circadian system and sleep , Impacts of home lighting on human health with children and adolescents most at risk from even low levels of light after dark thanks to a combination of the sensitivity of their visual system and changing hormone levels - Disruption of adolescents’ circadian clock: The vicious circle of media use, exposure to light at night, sleep loss and risk behaviors .?

This research gathered information about light levels in the bedrooms of over 3,000 older adults. Sleeping with light levels above 10 lux (that’s a very dim bedside lamp) significantly increases your risk of depressive symptoms compared to keeping the levels below 10 lux. Even 3 lux is enough to increase risk of sleep disturbance -?Associations between indoor light pollution and unhealthy outcomes in 2,947 adults: Cross-sectional analysis in the HEIJO-KYO cohort .?Just one night in 100 lux (a standard overhead light) is enough to increase heart rate variability and reduce insulin resistance the next day?-?Light exposure during sleep impairs cardiometabolic function .?

This paper mined over 85,000 biobank profiles to uncover a connection between levels of daylight and night time exposure and a range of conditions including self-harm and PTSD.? Those in the highest quartile of light exposure at night were at an average of 20% higher risk of? psychosis, while those in the highesst quartile for daytime light exposure had a 30% reduced risk of psychosis?-?Day and night light exposure are associated with psychiatric disorders: an objective light study in >85,000 people. ?

Schizophrenia is associated with severe sleep and circadian dysfunction, distress and depression. This brilliant paper used a combination of mathematical modelling with real world experiments. They discovered that the critical distinction between ‘normal’ controls and those with schizophrenia was not an intrinsic difference in their internal body clock, but significantly less exposure to bright light during the day (?>?500 lux), and variable exposure to light after dark. A simple lighting intervention to raise light levels during the day and reduce them at night effectively stabilised the sleep-wake cycle to a 24 hour pattern -?Extracting Circadian and Sleep Parameters from Longitudinal Data in Schizophrenia for the Design of Pragmatic Light Interventions .?

So what can you do?

1. Make sure you get outside during the day and boost with bright ‘cool’ lights, ideally before noon
2. Invest in super-warm lights for low-level lamps in the evening.
3. Use black-out curtains or blinds in the bedroom - or an eye-mask if that’s not an option