Embracing the light: a new way to study the effects of light exposure on mood
Scientists at the University of Manchester are investigating how mood is affected by different light exposure.
For those living under cloudy British skies, the fact that light affects mood is no surprise. Light is a powerful thing- it directly affects processes in the eyes and brain to give us sight and it plays an integral role in regulating circadian rhythms. It has many characteristics, including wavelength, and you are exposed to various amounts of each wavelength depending on your environment. As a result of its complexity, the way light is measured varies—you may be familiar with lux, lumen and even candles but arguably the best way of measuring the non-visual effects of light on humans is melanopic EDI (Equivalent Daylight Illuminance). You can find out more about this relatively new way of measuring light here. This is what a team of scientists from UoM including Chloe Roddis, Dr Nina Milosavljevic and Dr Beatriz Bano Otalora are tracking in their study, with collaboration from Dr Altug Didikoglu and a PhD studentship with Signify.
Image credit: Chloe Roddis
By attaching light monitors and fitness trackers to 50 people, Roddis has been working to identify the effects of different light exposure on mood. However, this isn’t a typical circadian experiment where people are locked in a cave, this is a naturalistic experiment in which all participants are free-range. Participants go about living their lives as normal. Measuring mood is a challenge in these conditions, so how is it done? For a subjective measure, individuals can simply track their mood on a scale-based questionnaire (how is your mood right now on a scale of 0 to 100, as an example, 0 meaning sad and 100 meaning happy?). For a more objective measure, Roddis has collaborated with Oxford’s Prof Catherine Harmer and Dr Amy Gillespie to select and adapt some artful tests. These detect something called affective bias—the tendency to prioritize the processing of negative events relative to positive events. Tests detecting affective bias are well established and validated; what Roddis has done is shortened and adapted them so they can be conducted repeatedly over several days. The question now is Will these shortened tests be just effective at detecting mood as the original full-length tests? If they are, then Roddis will be able to look at how both acute and historic light exposure impact affective bias.
After analysing the full data set to discover the acute effects and light history effects on mood and emotional bias, Roddis may continue her investigation to look at how light exposure affects mood in a cohort with a diagnosed mental health condition. In time, this will contribute to our understanding of how different light exposure impacts mood and mental health. Perhaps one day it will enable and empower organisations and individuals to tailor lighting so that we can make everyone just a little bit happier, regardless of the weather.
Lorena Rosen, edited by Chloe Roddis
26 November 2024